Range extraction

From Rosetta Code
Task
Range extraction
You are encouraged to solve this task according to the task description, using any language you may know.

A format for expressing an ordered list of integers is to use a comma separated list of either

  • individual integers
  • Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. (The range includes all integers in the interval including both endpoints)
  • The range syntax is to be used only for, and for every range that expands to more than two values.

Example
The list of integers:

-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20

Is accurately expressed by the range expression:

-6,-3-1,3-5,7-11,14,15,17-20

(And vice-versa).

Task
  • Create a function that takes a list of integers in increasing order and returns a correctly formatted string in the range format.
  • Use the function to compute and print the range formatted version of the following ordered list of integers. (The correct answer is: 0-2,4,6-8,11,12,14-25,27-33,35-39.)


    0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
   15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
   25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
   37, 38, 39
  • Show the output of your program.


Related task



Ada[edit]

The provided solutions return an empty string, if the Sequence of integers is empty. Ranges with negative bounds are represented as -9--4, as the task requires. For real-life applications it is better to use the notation -9..-4.

Iterative Solution[edit]

Since we don't know in advance how long the output will be, the iterative solution uses Unbounded_Strings.

with Ada.Text_IO;            use Ada.Text_IO;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Strings.Fixed; use Ada.Strings.Fixed;
 
procedure Range_Extraction is
type Sequence is array (Positive range <>) of Integer;
function Image (S : Sequence) return String is
Result : Unbounded_String;
From  : Integer;
procedure Flush (To : Integer) is
begin
if Length (Result) > 0 then
Append (Result, ',');
end if;
Append (Result, Trim (Integer'Image (From), Ada.Strings.Left));
if From < To then
if From+1 = To then
Append (Result, ',');
else
Append (Result, '-');
end if;
Append (Result, Trim (Integer'Image (To), Ada.Strings.Left));
end if;
end Flush;
begin
if S'Length > 0 then
From := S (S'First);
for I in S'First + 1..S'Last loop
if S (I - 1) + 1 /= S (I) then
Flush (S (I - 1));
From := S (I);
end if;
end loop;
Flush (S (S'Last));
end if;
return To_String (Result);
end Image;
begin
Put_Line
( Image
( ( 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
) ) );
end Range_Extraction;


Recursive Solution[edit]

The recursive solution avoids the usage of unbounded strings.

with Ada.Text_IO, Ada.Strings.Fixed;
 
procedure Range_Extract is
type Sequence is array (Positive range <>) of Integer;
 
function Img(I: Integer) return String is -- the image of an Integer
begin
return
Ada.Strings.Fixed.Trim(Integer'Image(I), Ada.Strings.Left);
end Img;
 
function Img(S: Sequence) return String is -- the image of a Sequence
 
function X(S : Sequence) return String is -- recursive eXtract
Idx: Positive := S'First;
begin
if S'Length = 0 then return
""; -- return nothing if Sequence is empty
else
while Idx < S'Last and then S(Idx+1) = S(Idx) + 1 loop
Idx := Idx + 1;
end loop;
if Idx = S'First then return
"," & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
elsif Idx = S'First+1 then return
"," & Img(S(S'First)) & ',' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
else return
"," & Img(S(S'First)) & '-' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
end if;
end if;
end X;
 
begin -- function Img(S: Sequence) return String
if S'Length = 0 then return
"";
else return
Img(S(S'First)) & X(S(S'First+1 .. S'Last));
end if;
end Img;
 
begin -- main
Ada.Text_IO.Put_Line(Img( ( 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29,
30, 31, 32, 33, 35, 36, 37, 38, 39) ));
end Range_Extract;
Output:

The sample output is exactly the same, for both solutions:

0-2,4,6-8,11,12,14-25,27-33,35-39

Aime[edit]

text
rp(...)
{
integer i, j;
data b;
text f;
 
i = 0;
j = 0;
while (i < count()) {
while (j < count() - 1) {
if (__integer($(j + 1)) == __integer($j) + 1) {
j += 1;
} else {
break;
}
}
if (i + 1 < j) {
b_form(b, "%s%d-%d", f, $i, $j);
f = ",";
} else {
while (i < j + 1) {
b_form(b, "%s%d", f, $i);
f = ",";
i += 1;
}
}
j += 1;
i = j;
}
 
return b_string(b);
}
 
integer
main(void)
{
o_form("%s\n", rp(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39));
 
return 0;
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

ALGOL 68[edit]

Note: The following Iterative code specimen is the "unrolled" version of the Generative code specimen below. Together they provided as a comparison of the two different methods.

Iterative[edit]

Works with: ALGOL 68 version Revision 1 - one minor extension to language used - PRAGMA READ, similar to C's #include directive.
Works with: ALGOL 68G version Any - tested with release algol68g-2.3.2.
  • The closest concept that Algol 68 has to duck typing is the tagged union. This is used to define mode urange = union(int, struct(int lwb, upb)). If duck typing was available it could reduced the size of the code specimen, but would have lost some of Algol 68's strong type data security.

File: Template_Range_extraction_Base.a68

###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
#
##
MODE SCALARLIST = FLEX[0]SCALAR;
MODE YIELDINT = PROC(SCALAR)VOID;
 
################################################################
# Declarations for manipulating lists of range pairs [lwb:upb] #
################################################################
MODE RANGE = STRUCT(SCALAR lwb, upb);
MODE RANGELIST = FLEX[0]RANGE;
MODE YIELDRANGE = PROC(RANGE)VOID;
 
PROC range repr = (RANGE range)STRING: (
STRING lwb := whole(lwb OF range,0);
IF lwb OF range = upb OF range THEN
lwb
ELSE
# "["+lwb+":"+whole(upb OF range,0)+"]" #
lwb+"-"+whole(upb OF range,0)
FI
);
 
# OP REPR = (RANGE range)STRING: range repr(range); # # firmly related to UNIRANGE #
 
######################################################################
# Declarations for manipulating lists containing pairs AND lone INTs #
######################################################################
MODE UNIRANGE = UNION(SCALAR, RANGE);
MODE UNIRANGELIST = FLEX[0]UNIRANGE;
MODE YIELDUNIRANGE = PROC(UNIRANGE)VOID;
 
PROC unirange repr = (UNIRANGE unirange)STRING:
CASE unirange IN
(RANGE range): range repr(range),
(SCALAR scalar): whole(scalar,0)
ESAC;
 
OP (UNIRANGE)STRING REPR = unirange repr; # alias #
 
# The closest thing Algol68 has to inheritance is the UNION #
MODE UNIRANGELISTS = UNION(UNIRANGELIST, RANGELIST, SCALARLIST);
 
PROC unirange list repr = (UNIRANGELIST unirange list)STRING: (
### Produce a STRING representation of a UNIRANGELIST ###
STRING out # := "("#, sep := "";
FOR key FROM LWB unirange list TO UPB unirange list DO
out +:= sep + REPR unirange list[key];
sep := "," # +" " #
OD;
out # +")" #
);
 
OP (UNIRANGELIST)STRING REPR = unirange list repr; # alias #
File: Template_Range_extraction_Iterative.a68
###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
#
##
PR READ "Template_Range_extraction_Base.a68" PR
 
OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = init unirange list; # alias #
 
PROC init unirange list = (UNIRANGELISTS unirange list)UNIRANGELIST: (
### Take a []SCALAR, []RANGE or []UNIRANGE, and return a normalised []UNIRANGE ###
 
INT len = UPB unirange list-LWB unirange list+1;
[LWB unirange list: LWB unirange list+len*2]UNIRANGE out unirange list;
SCALAR upb out unirange list := LWB out unirange list - 1;
UNION(VOID, RANGE) prev range := EMPTY;
 
PROC out unirange list append = (RANGE value)VOID:(
 
IF lwb OF value = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value
ELIF lwb OF value + 1 = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value;
out unirange list[upb out unirange list+:=1] := upb OF value
ELSE
out unirange list[upb out unirange list+:=1] := value
FI
);
 
FOR key FROM LWB unirange list TO UPB unirange list DO
UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
 
RANGE next range := CASE value IN
(RANGE range): range,
(SCALAR value): RANGE(value, value)
ESAC;
 
prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
out unirange list append(prev range);
next range
FI
OUT SKIP
ESAC
 
OD;
 
CASE prev range IN
(RANGE last range): out unirange list append(last range)
ESAC;
 
out unirange list[:upb out unirange list]
);
File: test_Range_extraction_Integer.a68
#!/usr/local/bin/a68g --script #
############################
# some simple test cases: #
############################
 
MODE SCALAR = INT;
PR READ "Template_Range_extraction_Iterative.a68" PR
#PR READ "Template_Range_extraction_Generative.a68" PR#
MODE RANGEINT = UNIRANGE;
 
test: BEGIN
[]INT int list = ( # unnormalised #
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
 
[]RANGE range list = ( # unnormalised #
(0,0), (1,1), (2,2), (4,4), (6,6), (7,7), (8,8), (11,11), (12,12), (14,14),
(15,15), (16,16), (17,17), (18,18), (19,19), (20,20), (21,21), (22,22), (23,23), (24,24),
(25,25), (27,27), (28,28), (29,29), (30,30), (31,31), (32,32), (33,33), (35,35), (36,36),
(37,37), (38,38), (39,39));
 
[]RANGEINT list a = ( # unnormalised #
RANGE(0,2), 4, RANGE(6,8), RANGE(11,12),
RANGE(14,25), RANGE(27,33), RANGE(35,39));
 
[]RANGEINT list b = ( # unnormalised #
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
 
[]RANGEINT list c = INITUNIRANGE(list b); # normalised #
 
# compare manipulation of various types of argument lists #
printf(($gl$,
REPR INITUNIRANGE int list,
REPR INITUNIRANGE range list,
REPR INITUNIRANGE list a,
REPR INITUNIRANGE list b,
REPR list c
))
END
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39

Generative[edit]

Works with: ALGOL 68 version Revision 1 - one minor extension to language used - PRAGMA READ, similar to C's #include directive.
Works with: ALGOL 68G version Any - tested with release algol68g-2.3.2.
  • The following code a set of helper functions/generators that can be used to manipulate a lists of ranges. They can manipulate either arrays or iterator. And they can handle data of type int or range and both these types unioned.

These chained iterators do the following steps:

  1. Iterate through three different types of initial arrays - []int, []range and []unirange with gen range, yielding range(lwb,upb)
  2. Iterate with gen range merge yielding merged range(lwb,upb)
  3. Iterate with gen unirange merge, merging and yielding a union of int and range
  4. Finally iterate with unirange list init exiting with an array of union of int and range.

File: Template_Range_extraction_Generative.a68

###
REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
#
##
PR READ "Template_Range_extraction_Base.a68" PR
 
PROC gen range = (UNIRANGELISTS unirange list, YIELDRANGE yield range)VOID:
### Take a []SCALAR, []RANGE or []URANGE, and generatively yield an unnormalised RANGE ###
 
FOR key FROM LWB unirange list TO UPB unirange list DO
# Note: Algol 68RS cannot handle LWB and UPB of a UNION in the following: #
UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
yield range(
CASE value IN
(RANGE range): range,
(SCALAR value): (value, value)
ESAC
)
OD;
 
PROC gen range merge = (UNIRANGELISTS unirange list, YIELDRANGE yield)VOID: (
### Take a []SCALAR, []RANGE or []URANGE , and generatively yield a normalised RANGE ###
 
UNION(VOID, RANGE) prev range := EMPTY;
 
# FOR RANGE next range IN # gen range(unirange list, # ) DO #
## (RANGE next range)VOID:
# if the ranges cannot be merge, then yield 1st, and return 2nd #
prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
#IF lwb OF prev range <= upb OF prev range THEN#
yield(prev range);
#FI;#
next range
FI
OUT SKIP
ESAC
# OD # );
 
CASE prev range IN (RANGE last range): yield(last range) ESAC
);
 
PROC gen unirange merge = (UNIRANGELISTS unirange list, YIELDUNIRANGE yield)VOID: (
### Take a []SCALAR, []RANGE or []UNIRANGE and generatively yield a normalised UNIRANGE ###
 
PROC unpack = (RANGE value)VOID:(
IF lwb OF value = upb OF value THEN
yield(lwb OF value)
ELIF lwb OF value + 1 = upb OF value THEN
yield(lwb OF value);
yield(upb OF value)
ELSE
yield(value)
FI
);
 
gen range merge(unirange list, unpack)
);
 
PROC unirange list init = (UNIRANGELISTS unirange list)UNIRANGELIST: (
### Take a []SCALAR, []RANGE or []UNIRANGE and return a static []UNIRANGE ###
 
INT len = UPB unirange list - LWB unirange list + 1;
[LWB unirange list: LWB unirange list + len * 2]UNIRANGE out unirange list; # estimate #
SCALAR upb out unirange list := LWB out unirange list - 1;
 
# FOR UNIRANGE unirange IN # gen unirange merge(unirange list, # ) DO #
## (UNIRANGE unirange)VOID:
out unirange list[upb out unirange list+:=1] := unirange
# OD # );
 
out unirange list[:upb out unirange list]
);
 
OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = unirange list init; # alias #
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39


AppleScript[edit]

Translation of: JavaScript
-- rangeFormat :: [Int] -> String
on rangeFormat(xs)
script rangeString
on |λ|(xs)
if length of xs > 2 then
(item 1 of xs as string) & "-" & (item -1 of xs as string)
else
intercalate(",", xs)
end if
end |λ|
end script
 
script nonConsec
on |λ|(a, b)
b - a > 1
end |λ|
end script
 
intercalate(",", map(rangeString, splitBy(nonConsec, xs)))
end rangeFormat
 
 
--TEST ------------------------------------------------------------------------
on run
set xs to {0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, ¬
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, ¬
33, 35, 36, 37, 38, 39}
 
rangeFormat(xs)
 
--> "0-2,4,6-8,11,12,14-25,27-33,35-39"
end run
 
 
-- GENERIC FUNCTIONS ----------------------------------------------------------
 
-- splitBy :: (a -> a -> Bool) -> [a] -> [[a]]
on splitBy(f, xs)
set mf to mReturn(f)
 
if length of xs < 2 then
{xs}
else
script p
on |λ|(a, x)
set {acc, active, prev} to a
if mf's |λ|(prev, x) then
{acc & {active}, {x}, x}
else
{acc, active & x, x}
end if
end |λ|
end script
 
set h to item 1 of xs
set lstParts to foldl(p, {{}, {h}, h}, items 2 thru -1 of xs)
item 1 of lstParts & {item 2 of lstParts}
end if
end splitBy
 
-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
tell mReturn(f)
set v to startValue
set lng to length of xs
repeat with i from 1 to lng
set v to |λ|(v, item i of xs, i, xs)
end repeat
return v
end tell
end foldl
 
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs, i, xs)
end repeat
return lst
end tell
end map
 
-- intercalate :: Text -> [Text] -> Text
on intercalate(strText, lstText)
set {dlm, my text item delimiters} to {my text item delimiters, strText}
set strJoined to lstText as text
set my text item delimiters to dlm
return strJoined
end intercalate
 
-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
if class of f is script then
f
else
script
property |λ| : f
end script
end if
end mReturn
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

AutoHotkey[edit]

msgbox % extract("0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39")
 
extract( list ) {
loop, parse, list, `,, %A_Tab%%A_Space%`r`n
{
if (A_LoopField+0 != p+1)
ret .= (f!=p ? (p>f+1 ? "-" : ",") p : "") "," f := A_LoopField
p := A_LoopField
}
return SubStr(ret (f!=p ? (p>f+1 ? "-" : ",") p : ""), 2)
}
Output:
---------------------------
Range extraction.ahk
---------------------------
0-2,4,6-8,11,12,14-25,27-33,35-39
---------------------------
OK   
---------------------------

AWK[edit]

AWK is a primitive bird that prefers global scope for arrays.

Local variables for functions are declared in the parameters and, by convention, separated from the expected ones by extra space.

#!/usr/bin/awk -f
 
BEGIN {
delete sequence
delete range
 
seqStr = "0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,"
seqStr = seqStr "25,27,28,29,30,31,32,33,35,36,37,38,39"
print "Sequence: " seqStr
fillSequence(seqStr)
rangeExtract()
showRange()
exit
}
 
function rangeExtract( runStart, runLen) {
delete range
runStart = 1
while(runStart <= length(sequence)) {
runLen = getSeqRunLen(runStart)
addRange(runStart, runLen)
runStart += runLen
}
}
 
function getSeqRunLen(startPos, pos) {
for (pos = startPos; pos < length(sequence); pos++) {
if (sequence[pos] + 1 != sequence[pos + 1]) break;
}
return pos - startPos + 1;
}
 
function addRange(startPos, len, str) {
if (len == 1) str = sequence[startPos]
else if (len == 2) str = sequence[startPos] "," sequence[startPos + 1]
else str = sequence[startPos] "-" sequence[startPos + len - 1]
range[length(range) + 1] = str
}
 
function showRange( r) {
printf " Ranges: "
for (r = 1; r <= length(range); r++) {
if (r > 1) printf ","
printf range[r]
}
printf "\n"
}
 
function fillSequence(seqStr, n, s) {
n = split(seqStr,a,/[,]+/)
for (s = 1; s <= n; s++) {
sequence[s] = a[s]
}
}
Output:
 Sequence: 0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
   Ranges: 0-2,4,6-8,11,12,14-25,27-33,35-39

BBC BASIC[edit]

      range$ = " 0,  1,  2,  4,  6,  7,  8, 11, 12, 14, " + \
\ "15, 16, 17, 18, 19, 20, 21, 22, 23, 24, " + \
\ "25, 27, 28, 29, 30, 31, 32, 33, 35, 36, " + \
\ "37, 38, 39"
PRINT FNrangeextract(range$)
END
 
DEF FNrangeextract(r$)
LOCAL f%, i%, r%, t%, t$
f% = VAL(r$)
REPEAT
i% = INSTR(r$, ",", i%+1)
t% = VALMID$(r$, i%+1)
IF t% = f% + r% + 1 THEN
r% += 1
ELSE
CASE r% OF
WHEN 0: t$ += STR$(f%) + ","
WHEN 1: t$ += STR$(f%) + "," + STR$(f% + r%) + ","
OTHERWISE: t$ += STR$(f%) + "-" + STR$(f% + r%) + ","
ENDCASE
r% = 0
f% = t%
ENDIF
UNTIL i% = 0
= LEFT$(t$)
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Bracmat[edit]

  ( rangeExtract
= accumulator firstInRange nextInRange
, accumulate fasten rangePattern
. ( accumulate
=  !accumulator
(!accumulator:|?&",")
 !firstInRange
(  !firstInRange+1:<>!nextInRange
& ( !firstInRange+2:!nextInRange&","
| "-"
)
-1+!nextInRange
|
)
 : ?accumulator
)
& ( fasten
= [%( !accumulate
& (!sjt:?firstInRange)+1:?nextInRange
)
)
& ( rangePattern
= (
|  ?
( !nextInRange
& 1+!nextInRange:?nextInRange
)
)
( &!accumulate
| (#<>!nextInRange:!fasten) !rangePattern
)
)
& :?accumulator:?firstInRange
& !arg:(|#!fasten !rangePattern)
& str$!accumulator
)
& ( test
= L A
. put$(!arg " ==>\n",LIN)
& (  !arg:(?,?)
& whl'(!arg:(?A,?arg)&(!A,!L):?L)
& whl'(!L:(?A,?L)&!A !arg:?arg)
|
)
& out$(rangeExtract$!arg)
)
& test
$ (0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39)
Output:
(0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39)  ==>
0-2,4,6-8,11,12,14-25,27-33,35-39

C[edit]

Using the fine tradition of snprintf, rprint is not responsible for allocating output buffer. It prints the range only if supplied a non-null pointer, but always returns the output length sans the terminating null, so caller can allocate buffer.

#include <stdio.h>
#include <stdlib.h>
 
size_t rprint(char *s, int *x, int len)
{
#define sep (a > s ? "," : "") /* use comma except before first output */
#define ol (s ? 100 : 0) /* print only if not testing for length */
int i, j;
char *a = s;
for (i = j = 0; i < len; i = ++j) {
for (; j < len - 1 && x[j + 1] == x[j] + 1; j++);
 
if (i + 1 < j)
a += snprintf(s?a:s, ol, "%s%d-%d", sep, x[i], x[j]);
else
while (i <= j)
a += snprintf(s?a:s, ol, "%s%d", sep, x[i++]);
}
return a - s;
#undef sep
#undef ol
}
 
int main()
{
int x[] = { 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 };
 
char *s = malloc(rprint(0, x, sizeof(x) / sizeof(int)) + 1);
rprint(s, x, sizeof(x) / sizeof(int));
printf("%s\n", s);
 
return 0;
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

C++[edit]

 
#include <iostream>
#include <iterator>
#include <cstddef>
 
template<typename InIter>
void extract_ranges(InIter begin, InIter end, std::ostream& os)
{
if (begin == end)
return;
 
int current = *begin++;
os << current;
int count = 1;
 
while (begin != end)
{
int next = *begin++;
if (next == current+1)
++count;
else
{
if (count > 2)
os << '-';
else
os << ',';
if (count > 1)
os << current << ',';
os << next;
count = 1;
}
current = next;
}
 
if (count > 1)
os << (count > 2? '-' : ',') << current;
}
 
template<typename T, std::size_t n>
T* end(T (&array)[n])
{
return array+n;
}
 
int main()
{
int data[] = { 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 };
 
extract_ranges(data, end(data), std::cout);
std::cout << std::endl;
}
 
Output:
 0-2,4,6-8,11,12,14-25,27-33,35-39

C#[edit]

using System;
using System.Collections.Generic;
using System.Linq;
 
class RangeExtraction
{
static void Main()
{
const string testString = "0, 1, 2, 4, 6, 7, 8, 11, 12, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 27, 28, 29, 30, 31, 32, 33, 35, 36,37, 38, 39";
var result = String.Join(",", RangesToStrings(GetRanges(testString)));
Console.Out.WriteLine(result);
}
 
public static IEnumerable<IEnumerable<int>> GetRanges(string testString)
{
var numbers = testString.Split(new[] { ',' }).Select(x => Convert.ToInt32(x));
var current = new List<int>();
foreach (var n in numbers)
{
if (current.Count == 0)
{
current.Add(n);
}
else
{
if (current.Max() + 1 == n)
{
current.Add(n);
}
else
{
yield return current;
current = new List<int> { n };
}
}
}
yield return current;
}
 
public static IEnumerable<string> RangesToStrings(IEnumerable<IEnumerable<int>> ranges)
{
foreach (var range in ranges)
{
if (range.Count() == 1)
{
yield return range.Single().ToString();
}
else if (range.Count() == 2)
{
yield return range.Min() + "," + range.Max();
}
else
{
yield return range.Min() + "-" + range.Max();
}
}
}
}
 
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

C#: Alternate Version[edit]

This example is incorrect. Please fix the code and remove this message.
Details: 11-12 is wrong. Check the spec.
using System;
using System.Collections.Generic;
using System.Linq;
 
namespace RangeExtraction {
internal static class ListExtensions {
internal static string ExtractRange(this IEnumerable<int> values) {
var list = values.Distinct().OrderBy(_ => _).ToArray();
var ranges = new int[0][].AsEnumerable();
var current = 0;
for (var i = 1; ; ++i) {
if (i >= list.Length) {
ranges = ranges.Concat(new[] { new[] { i != current ? current : i - 1, i - 1 } });
break;
}
if (list[i] == list[i - 1] + 1)
continue;
ranges = ranges.Concat(new[] { new[] { current, i - 1 } });
current = i;
}
return string.Join(",", ranges.Select(r => string.Format(r[0] == r[1] ? "{0}" : "{0}-{1}", list[r[0]], list[r[1]])));
}
}
 
internal class Program {
private static readonly IList<int> VALUES = new[] {
0, 1, 2,
4,
6, 7, 8,
11, 12,
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
27, 28, 29, 30, 31, 32, 33,
35, 36, 37, 38, 39
};
 
private static void Main(string[] args) {
var rangestr = VALUES.ExtractRange();
Console.WriteLine("values: {{{0}}}", string.Join(", ", VALUES.Select(_=>_.ToString())));
Console.WriteLine("\r\nranges = \"{0}\"", rangestr);
}
}
}
Output:
values: {0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}
ranges = "0-2,4,6-8,11-12,14-25,27-33,35-39"

Ceylon[edit]

shared void run() {
 
value numbers = [
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
];
 
function asRangeFormattedString<Value>([Value*] values)
given Value satisfies Enumerable<Value> {
 
value builder = StringBuilder();
 
void append(Range<Value> range) {
if(!builder.empty) {
builder.append(",");
}
if(1 <= range.size < 3) {
builder.append(",".join(range));
} else {
builder.append("``range.first``-``range.last``");
}
}
 
if(nonempty values) {
variable value currentRange = values.first..values.first;
for(val in values.rest) {
if(currentRange.last.successor == val) {
currentRange = currentRange.first..val;
} else {
append(currentRange);
currentRange = val..val;
}
}
append(currentRange);
}
return builder.string;
}
 
value rangeString = asRangeFormattedString(numbers);
assert(rangeString == "0-2,4,6-8,11,12,14-25,27-33,35-39");
print(rangeString);
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

COBOL[edit]

Works with: OpenCOBOL
       IDENTIFICATION DIVISION.
PROGRAM-ID. extract-range-task.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 data-str PIC X(200) VALUE "0, 1, 2, 4, 6,"
& " 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, "
& "24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39".
 
01 result PIC X(200).
 
PROCEDURE DIVISION.
CALL "extract-range" USING CONTENT data-str, REFERENCE result
DISPLAY FUNCTION TRIM(result)
 
GOBACK
.
END PROGRAM extract-range-task.
 
 
IDENTIFICATION DIVISION.
PROGRAM-ID. extract-range.
 
DATA DIVISION.
LOCAL-STORAGE SECTION.
COPY "nums-table.cpy".
 
01 difference PIC 999.
 
01 rng-begin PIC S999.
01 rng-end PIC S999.
 
01 num-trailing PIC 999.
 
01 trailing-comma-pos PIC 999.
 
LINKAGE SECTION.
01 nums-str PIC X(200).
01 extracted-range PIC X(200).
 
01 extracted-range-len CONSTANT LENGTH extracted-range.
 
PROCEDURE DIVISION USING nums-str, extracted-range.
CALL "split-nums" USING CONTENT nums-str, ", ",
REFERENCE nums-table
 
*> Process the table
MOVE nums (1) TO rng-begin
PERFORM VARYING nums-idx FROM 2 BY 1
UNTIL num-nums < nums-idx
SUBTRACT nums (nums-idx - 1) FROM nums (nums-idx)
GIVING difference
 
*> If number is more than one away from the previous one
*> end the range and start a new one.
IF difference > 1
MOVE nums (nums-idx - 1) TO rng-end
CALL "add-next-range" USING CONTENT rng-begin,
rng-end, REFERENCE extracted-range
MOVE nums (nums-idx) TO rng-begin
END-IF
END-PERFORM
 
*> Process the last number
MOVE nums (num-nums) TO rng-end
CALL "add-next-range" USING CONTENT rng-begin,
rng-end, REFERENCE extracted-range
 
*> Remove trailing comma.
CALL "find-num-trailing-spaces"
USING CONTENT extracted-range, REFERENCE num-trailing
COMPUTE trailing-comma-pos =
extracted-range-len - num-trailing
MOVE SPACE TO extracted-range (trailing-comma-pos:1)
 
GOBACK
.
 
IDENTIFICATION DIVISION.
PROGRAM-ID. split-nums INITIAL.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 num-len PIC 9.
01 next-num-pos PIC 999.
 
LINKAGE SECTION.
01 str PIC X(200).
01 delim PIC X ANY LENGTH.
 
COPY "nums-table.cpy".
 
PROCEDURE DIVISION USING str, delim, nums-table.
INITIALIZE num-nums
 
PERFORM UNTIL str = SPACES
INITIALIZE num-len
INSPECT str TALLYING num-len FOR CHARACTERS BEFORE delim
 
ADD 1 TO num-nums
 
*> If there are no more instances of delim in the string,
*> add the rest of the string to the last element of the
*> table.
IF num-len = 0
MOVE str TO nums (num-nums)
EXIT PERFORM
ELSE
MOVE str (1:num-len) TO nums (num-nums)
ADD 3 TO num-len GIVING next-num-pos
MOVE str (next-num-pos:) TO str
END-IF
END-PERFORM
.
END PROGRAM split-nums.
 
IDENTIFICATION DIVISION.
PROGRAM-ID. add-next-range INITIAL.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 num-trailing PIC 999.
01 start-pos PIC 999.
 
01 range-len PIC 999.
 
01 begin-edited PIC -ZZ9.
01 end-edited PIC -ZZ9.
 
LINKAGE SECTION.
01 rng-begin PIC S999.
01 rng-end PIC S999.
 
01 extracted-range PIC X(200).
 
01 extracted-range-len CONSTANT LENGTH extracted-range.
 
PROCEDURE DIVISION USING rng-begin, rng-end, extracted-range.
CALL "find-num-trailing-spaces"
USING CONTENT extracted-range, REFERENCE num-trailing
COMPUTE start-pos = extracted-range-len - num-trailing + 1
 
SUBTRACT rng-begin FROM rng-end GIVING range-len
 
MOVE rng-begin TO begin-edited
MOVE rng-end TO end-edited
 
EVALUATE TRUE
WHEN rng-begin = rng-end
STRING FUNCTION TRIM(begin-edited), ","
INTO extracted-range (start-pos:)
 
WHEN range-len = 1
STRING FUNCTION TRIM(begin-edited), ",",
FUNCTION TRIM(end-edited), ","
INTO extracted-range (start-pos:)
 
WHEN OTHER
STRING FUNCTION TRIM(begin-edited), "-",
FUNCTION TRIM(end-edited), ","
INTO extracted-range (start-pos:)
END-EVALUATE
.
END PROGRAM add-next-range.
 
IDENTIFICATION DIVISION.
PROGRAM-ID. find-num-trailing-spaces.
 
DATA DIVISION.
LINKAGE SECTION.
01 str PIC X(200).
01 num-trailing PIC 999.
 
PROCEDURE DIVISION USING str, num-trailing.
INITIALIZE num-trailing
INSPECT str TALLYING num-trailing FOR TRAILING SPACES
.
END PROGRAM find-num-trailing-spaces.
 
END PROGRAM extract-range.

nums-table.cpy:

       01  nums-table.
03 num-nums PIC 999.
03 nums-area.
05 nums PIC S999 OCCURS 1 TO 100 TIMES
DEPENDING ON num-nums
INDEXED BY nums-idx.
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Common Lisp[edit]

(defun format-with-ranges (list)
(unless list (return ""))
(with-output-to-string (s)
(let ((current (first list))
(list (rest list))
(count 1))
(princ current s)
(dolist (next list)
(if (= next (1+ current))
(incf count)
(progn (princ (if (> count 2) "-" ",") s)
(when (> count 1)
(princ current s)
(princ "," s))
(princ next s)
(setf count 1)))
(setf current next))
(when (> count 1)
(princ (if (> count 2) "-" ",") s)
(princ current s)))))
 
CL-USER> (format-with-ranges (list 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
"0-2,4,6-8,11,12,14-25,27-33,35-39"
 

D[edit]

import std.stdio, std.conv, std.string, std.algorithm, std.range;
 
string rangeExtraction(in int[] items)
in {
assert(items.isSorted);
} body {
if (items.empty)
return null;
auto ranges = [[items[0].text]];
 
foreach (immutable x, immutable y; items.zip(items[1 .. $]))
if (x + 1 == y)
ranges[$ - 1] ~= y.text;
else
ranges ~= [y.text];
 
return ranges
.map!(r => r.length > 2 ? r[0] ~ "-" ~ r.back : r.join(','))
.join(',');
}
 
void main() {
foreach (data; [[-8, -7, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9,
10, 11, 14, 15, 17, 18, 19, 20],
[0, 0, 0, 1, 1],
[0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31,
32, 33, 35, 36, 37, 38, 39]])
data.rangeExtraction.writeln;
}
Output:
-8--6,-3-1,3-5,7-11,14,15,17-20
0,0,0,1,1
0-2,4,6-8,11,12,14-25,27-33,35-39

DWScript[edit]

procedure ExtractRanges(const values : array of Integer);
begin
var i:=0;
while i<values.Length do begin
if i>0 then
Print(',');
Print(values[i]);
var j:=i+1;
while (j<values.Length) and (values[j]=values[j-1]+1) do
Inc(j);
Dec(j);
if j>i then begin
if j=i+1 then
Print(',')
else Print('-');
Print(values[j]);
end;
i:=j+1;
end;
end;
 
ExtractRanges([ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]);
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

E[edit]

Cheeky solution: relying on the standard library for finding ranges, and just formatting them ourselves.

def rex(numbers :List[int]) {
var region := 0..!0
for n in numbers { region |= n..n }
var ranges := []
for interval in region.getSimpleRegions() {
def a := interval.getOptStart()
def b := interval.getOptBound() - 1
ranges with= if (b > a + 1) {
`$a-$b`
} else if (b <=> a + 1) {
`$a,$b`
} else { # b <=> a
`$a`
}
}
return ",".rjoin(ranges)
}
? rex([
> 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
> 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
> 25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
> 37, 38, 39])
# value: "0-2,4,6-8,11,12,14-25,27-33,35-39"
 

EchoLisp[edit]

 
(define task '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39))
 
;; 1- GROUPING
(define (group-range item acc)
(if
(or (empty? acc) (!= (caar acc) (1- item)))
(cons (cons item item) acc)
(begin (set-car! (car acc) item) acc)))
 
;; intermediate result
;; (foldl group-range () task)
;; → ((39 . 35) (33 . 27) (25 . 14) (12 . 11) (8 . 6) (4 . 4) (2 . 0))
 
;; 2- FORMATTING
(define (range->string range)
(let ((from (rest range)) (to (first range)))
(cond
((= from to) (format "%d " from))
((= to (1+ from)) (format "%d, %d " from to))
(else (format "%d-%d " from to)))))
 
;; 3 - FINAL
(string-join (map range->string (reverse (foldl group-range () task))) ",")
"0-2 ,4 ,6-8 ,11, 12 ,14-25 ,27-33 ,35-39 "
 

Eiffel[edit]

 
class
RANGE
 
create
make
 
feature
make
local
extended_range: STRING
do
extended_range := "0, 1, 2, 4, 6, 7, 8, 11, 12, 14, " +
"15, 16, 17, 18, 19, 20, 21, 22, 23, 24, " +
"25, 27, 28, 29, 30, 31, 32, 33, 35, 36, " +
"37, 38, 39"
print("Extended range: " + extended_range + "%N")
print("Extracted range: " + extracted_range(extended_range) + "%N%N")
end
 
feature
extracted_range(sequence: STRING): STRING
local
elements: LIST[STRING]
first, curr: STRING
subrange_size, index: INTEGER
do
sequence.replace_substring_all (", ", ",")
elements := sequence.split (',')
from
index := 2
first := elements.at (1)
subrange_size := 0
Result := ""
until
index > elements.count
loop
curr := elements.at (index)
if curr.to_integer - first.to_integer - subrange_size = 1
then
subrange_size := subrange_size + 1
else
Result.append(first)
if (subrange_size <= 1)
then
Result.append (", ")
else
Result.append (" - ")
end
if (subrange_size >= 1)
then
Result.append ((first.to_integer + subrange_size).out)
Result.append (", ")
end
 
first := curr
subrange_size := 0
end
index := index + 1
end
Result.append(first)
if (subrange_size <= 1)
then
Result.append (", ")
else
Result.append (" - ")
end
if (subrange_size >= 1)
then
Result.append ((first.to_integer + subrange_size).out)
end
end
end
 
Output:
Extended range: 0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
Extracted range: 0 - 2,  4,  6 - 8, 11, 12, 14 - 25, 27 - 33, 35 - 39

Elixir[edit]

Translation of: Ruby
defmodule RC do
def range_extract(list) do
max = Enum.max(list) + 2
sorted = Enum.sort([max|list])
candidate_number = hd(sorted)
current_number = hd(sorted)
extract(tl(sorted), candidate_number, current_number, [])
end
 
defp extract([], _, _, range), do: Enum.reverse(range) |> Enum.join(",")
defp extract([next|rest], candidate, current, range) when current+1 >= next do
extract(rest, candidate, next, range)
end
defp extract([next|rest], candidate, current, range) when candidate == current do
extract(rest, next, next, [to_string(current)|range])
end
defp extract([next|rest], candidate, current, range) do
separator = if candidate+1 == current, do: ",", else: "-"
str = "#{candidate}#{separator}#{current}"
extract(rest, next, next, [str|range])
end
end
 
list = [
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
]
IO.inspect RC.range_extract(list)
Output:
"0-2,4,6-8,11,12,14-25,27-33,35-39"

Emacs Lisp[edit]

version 1[edit]

 
(require 'gnus-range)
(defun rangext (lst)
(mapconcat (lambda (item)
(if (consp item)
(if (= (+ 1 (car item) ) (cdr item) )
(format "%d,%d" (car item) (cdr item) )
(format "%d-%d" (car item) (cdr item) ))
(format "%d" item)))
(gnus-compress-sequence lst)
","))
 
(insert (rangext '(0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39) ))
 

Output:

0-2,4,6-8,11,12,14-25,27-33,35-39

version 2[edit]

 
(setq max-lisp-eval-depth 10000)
 
(defun ab (a ls)
(if ls (if (= (+ a 1) (car ls) )
(abc a (car ls) (cdr ls) )
(format "%d,%s" a (ab (car ls) (cdr ls) )))
(format "%d" a) ))
 
(defun abc (a b ls)
(if ls (if (= (+ b 1) (car ls) )
(abcd a (car ls) (cdr ls) )
(format "%d,%d,%s" a b (ab (car ls) (cdr ls) )))
(format "%d,%d" a b) ))
 
(defun abcd (a c ls)
(if ls (if (= (+ c 1) (car ls) )
(abcd a (car ls) (cdr ls) )
(format "%d-%d,%s" a c (ab (car ls) (cdr ls) )))
(format "%d-%d" a c) ))
 
(defun rangext (ls)
(if ls (ab (car ls) (cdr ls) ) ""))
 
(insert (rangext '(0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39) ))
 

Output:

0-2,4,6-8,11,12,14-25,27-33,35-39

Erlang[edit]

 
-module( range ).
 
-export( [extraction/1, task/0] ).
 
extraction( [H | T] ) when is_integer(H) ->
Reversed_extracts = extraction_acc( lists:foldl(fun extraction/2, {H, []}, T) ),
string:join( lists:reverse(Reversed_extracts), "," ).
 
task() ->
io:fwrite( "~p~n", [extraction([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39])] ).
 
 
 
extraction( N, {Start, Acc} ) when N =:= Start + 1 -> {Start, N, Acc};
extraction( N, {Start, Acc} ) -> {N, extraction_acc( {Start, Acc} )};
extraction( N, {Start, Stop, Acc} ) when N =:= Stop + 1 -> {Start, N, Acc};
extraction( N, {Start, Stop, Acc} ) -> {N, extraction_acc( {Start, Stop, Acc} )}.
 
extraction_acc( {N, Acc} ) -> [erlang:integer_to_list(N) | Acc];
extraction_acc( {Start, Stop, Acc} ) when Stop > Start + 1 -> [erlang:integer_to_list(Start) ++ "-" ++ erlang:integer_to_list(Stop) | Acc];
extraction_acc( {Start, Stop, Acc} ) -> [erlang:integer_to_list(Stop), erlang:integer_to_list(Start) | Acc]. % Reversed
 
Output:
19> range:task().
"0-2,4,6-8,11,12,14-25,27-33,35-39"

Euphoria[edit]

function extract_ranges(sequence s)
integer first
sequence out
out = ""
if length(s) = 0 then
return out
end if
first = 1
for i = 2 to length(s) do
if s[i] != s[i-1]+1 then
if first = i-1 then
out &= sprintf("%d,", s[first])
elsif first = i-2 then
out &= sprintf("%d,%d,", {s[first],s[i-1]})
else
out &= sprintf("%d-%d,", {s[first],s[i-1]})
end if
first = i
end if
end for
if first = length(s) then
out &= sprintf("%d", s[first])
elsif first = length(s)-1 then
out &= sprintf("%d,%d", {s[first],s[$]})
else
out &= sprintf("%d-%d", {s[first],s[$]})
end if
return out
end function
 
puts(1, extract_ranges({0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}))
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

F#[edit]

let extractRanges = function
| [] -> Seq.empty
| x::xr ->
let rec loop ys first last = seq {
match ys with
| y::yr when y = last + 1 -> yield! loop yr first y // add to current range
| y::yr -> yield (first, last) // finish current range
yield! loop yr y y // and start next
| [] -> yield (first, last) } // finish final range
loop xr x x
 
 
let rangeToString (s,e) =
match e-s with
| 0 -> sprintf "%d" s
| 1 -> sprintf "%d,%d" s e
| _ -> sprintf "%d-%d" s e
 
 
let extract = extractRanges >> Seq.map rangeToString >> String.concat ","
 
 
printfn "%s" (extract [ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;
22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ])
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Forth[edit]

create values
here
0 , 1 , 2 , 4 , 6 , 7 , 8 , 11 , 12 , 14 ,
15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ,
25 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 35 , 36 ,
37 , 38 , 39 ,
here swap - 1 cells / constant /values
 
: clip 1- swap cell+ swap ; \ reduce array
: .range2 0 .r ." -" 0 .r ; \ difference two or more
: .range1 0 .r ." , " 0 .r ; \ difference one
: .range0 drop 0 .r ; \ no difference
\ select printing routine
create .range ' .range0 , ' .range1 , ' .range2 ,
does> >r over over - 2 min cells r> + @ execute ;
 
: .ranges ( a n --)
over @ dup >r >r \ setup first value
begin
clip dup \ check length array
while
over @ dup [email protected] 1+ = \ check if range breaks
if r> drop >r else r> r> .range ." , " dup >r >r then
repeat 2drop r> r> .range cr \ print last range
;
 
values /values .ranges
Output:
0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39

Fortran[edit]

There was some initial confusion as to whether the list was to be supplied as an array of integer values, or as a text string from which integer values were to be extracted. The consensus is a text string. In principle the text string could be parsed to find the starting and stopping positions of each number so that any size integers could be processed merely by copying the texts around without reading the values into integer variables of limited capacity, but that would be complicated by the possible presence of signs. So, it was simpler to take advantage of the free-format data reading protocol that would handle signs without difficulty and on output any spurious +signs would be omitted. This however immediately raises the question: how many numbers are there to be read? A very useful input style is to start with the number of values to read followed by the values; then something like READ(IN,*) N,A(1:N) works nicely. But this is not the given style of input, so a fallback: count how many commas appear to deduce how many numbers there are to be read. The free-format style allows either commas or spaces between numbers (and if there is a comma, any spaces also present are passed by), so the layout is easy. Data errors could still be encountered, so a more complete version would have READ (TEXT,*,ERR=label) VAL(1:N) to catch these, but the specification does not call for checking.

The standard problem is "how long is a piece of string?" - arrays normally must be given a specific bound. With F90, it is possible to allocate an array of a size determined at run time via some tedious gibberish, but for this example, LOTS will suffice. More seriously, the specification calls for a function returning the text representation of the list, but unfortunately, a function must have a specified size as in CHARACTER*66 FUNCTION IRANGE(TEXT) where the 66 is fixed at compile time. With Fortran 2003, there are facilities for the run-time sizing of character variables, but not in F90/95 though they could be devised with a great deal of blather. In any case, the size required is not known until the end, so successively reallocating space of size 1, 2, 3, 4, ... and each time copying the existing text into the larger text area would soon be painful. A largeish value for the size of the result could be used but instead, a subroutine, which returns its result via modifying its parameter. It is up to the caller to provide a parameter of sufficient size.

Although Pascal offers a Str procedure for converting a variable to a text string, maddeningly, it is a procedure not a function and so cannot be used within a compound statement. Fortran could offer access to the FORMAT facility via something like a function FMT(x) which returns the text representation of variable x with no leading or trailing spaces (whereby FMT(-6) would return "-6" and so forth) but alas, does not. Such a function cannot be written in ordinary Fortran until such time as it is possible to return varying-sized character results. The I0 format code standardised in F90 comes close but of course it must be used in a complex environment. All in all, it is easier to devise a subroutine SPLOT(n) to write the value of an integer (with possible leading hyphen if negative) to a scratchpad and then EMIT its text character by character to the output variable character until stopped by a space. Subroutines EMIT and SPLOT could be normal separate subroutines, but as servants of IRANGE it is easier to take advantage of the F90 facility whereby they can be "contained" inside IRANGE and thereby gain access to its internal context. Otherwise, there would have to be additional parameters or usage of COMMON variables for such communication.

The method grinds through the list of values, looking ahead for consecutive continuations (relying on the value of a DO-loop's index variable being available on exit from the loop) and thereby placing in its output string either a range of numbers or a single number. This could be done by using WRITE with suitable FORMAT statements to appropriate portions of the output string via careful counting of positions, but using EMIT and SPLOT avoids the requisite cogitations. A fancier method would be to devise a list of numbers to be output along with a suitable FORMAT statement that would supply the commas and hyphens as appropriate. Of course, one would again face the question "how long is a FORMAT string?", so, grinding stepwise it is.
      SUBROUTINE IRANGE(TEXT)	!Identifies integer ranges in a list of integers.
Could make this a function, but then a maximum text length returned would have to be specified.
CHARACTER*(*) TEXT !The list on input, the list with ranges on output.
INTEGER LOTS !Once again, how long is a piece of string?
PARAMETER (LOTS = 666) !This should do, at least for demonstrations.
INTEGER VAL(LOTS) !The integers of the list.
INTEGER N !Count of numbers.
INTEGER I,I1 !Steppers.
N = 1 !Presume there to be one number.
DO I = 1,LEN(TEXT) !Then by noticing commas,
IF (TEXT(I:I).EQ.",") N = N + 1 !Determine how many more there are.
END DO !Step alonmg the text.
IF (N.LE.2) RETURN !One comma = two values. Boring.
IF (N.GT.LOTS) STOP "Too many values!"
READ (TEXT,*) VAL(1:N) !Get the numbers, with free-format flexibility.
TEXT = "" !Scrub the parameter!
L = 0 !No text has been placed.
I1 = 1 !Start the scan.
10 IF (L.GT.0) CALL EMIT(",") !A comma if there is prior text.
CALL SPLOT(VAL(I1)) !The first number always appears.
DO I = I1 + 1,N !Now probe ahead
IF (VAL(I - 1) + 1 .NE. VAL(I)) EXIT !While values are consecutive.
END DO !Up to the end of the remaining list.
IF (I - I1 .GT. 2) THEN !More than two consecutive values seen?
CALL EMIT("-") !Yes!
CALL SPLOT(VAL(I - 1)) !The ending number of a range.
I1 = I !Finger the first beyond the run.
ELSE !But if too few to be worth a span,
I1 = I1 + 1 !Just finger the next number.
END IF !So much for that starter.
IF (I.LE.N) GO TO 10 !Any more?
CONTAINS !Some assistants to save on repetition.
SUBROUTINE EMIT(C) !Rolls forth one character.
CHARACTER*1 C !The character.
L = L + 1 !Advance the finger.
IF (L.GT.LEN(TEXT)) STOP "Ran out of text!" !Maybe not.
TEXT(L:L) = C !And place the character.
END SUBROUTINE EMIT !That was simple.
SUBROUTINE SPLOT(N) !Rolls forth a signed number.
INTEGER N !The number.
CHARACTER*12 FIELD !Sufficient for 32-bit integers.
INTEGER I !A stepper.
WRITE (FIELD,"(I0)") N!Roll the number, with trailing spaces.
DO I = 1,12 !Now transfer the text of the number.
IF (FIELD(I:I).LE." ") EXIT !Up to the first space.
CALL EMIT(FIELD(I:I)) !One by one.
END DO !On to the end.
END SUBROUTINE SPLOT !Not so difficult either.
END !So much for IRANGE.
 
PROGRAM POKE
CHARACTER*(200) SOME
SOME = " 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, "
1 //" 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,"
2 //"25, 27, 28, 29, 30, 31, 32, 33, 35, 36, "
3 //"37, 38, 39 "
CALL IRANGE(SOME)
WRITE (6,*) SOME
END
Output: spaces after the commas could be added easily enough.
 0-2,4,6-8,11,12,14-25,27-33,35-39

FreeBASIC[edit]

' FB 1.05.0 Win64
 
Function formatRange (a() As Integer) As String
Dim lb As Integer = LBound(a)
Dim ub As Integer = UBound(a)
If ub = - 1 Then Return ""
If lb = ub Then Return Str(a(lb))
Dim rangeCount As Integer = 1
Dim range As String = Str(a(lb))
For i As Integer = lb + 1 To ub
If a(i) = a(i - 1) + 1 Then
rangeCount += 1
ElseIf rangeCount = 1 Then
range += "," + Str(a(i))
ElseIf rangeCount = 2 Then
rangeCount = 1
range += "," + Str(a(i-1)) + "," + Str(a(i))
Else
rangeCount = 1
range += "-" + Str(a(i-1)) + "," + Str(a(i))
End If
Next
If rangeCount = 2 Then
range += "," + Str(a(ub))
ElseIf rangeCount > 2 Then
range += "-" + Str(a(ub))
End If
Return range
End Function
 
Dim a(1 To 20) As Integer = {-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20}
Print formatRange(a())
Print
 
Dim b(1 To 33) As Integer => _
{ _
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, _
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, _
25, 27, 28, 29, 30, 31, 32, 33, 35, 36, _
37, 38, 39 _
}
 
Print formatRange(b())
Print
Print "Press any key to continue"
Sleep
Output:
-6,-3-1,3-5,7-11,14,15,17-20

0-2,4,6-8,11,12,14-25,27-33,35-39

Gambas[edit]

Click this link to run this code

siInput As New Short[]
siInput1 As Short[] = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]
siInput2 As Short[] = [-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20]
sOutput As New String[]
siCount As Short
siNum As Short
'__________________
Public Sub Main()
Dim siLoop As Short
 
For siLoop = 0 To 1
If siLoop = 0 Then siInput = siInput1.Copy() Else siInput = siInput2.Copy()
siCount = 0
siNum = 0
Repeat
If siInput[siCount + 1] = siInput[siCount] + 1 Then
Inc siCount
Else
GetOutput
Endif
Until siCount = siInput.Max
 
GetOutput
Print sOutput.join(", ")
sOutput.clear
Next
 
End
'__________________
Public Sub GetOutput()
 
If siNum = siCount Then
sOutput.add(siInput[siNum])
Inc siCount
siNum = siCount
End If
 
If siNum <> siCount Then
If siNum = siCount - 1 Then
sOutput.add(siInput[siNum])
sOutput.add(siInput[siNum + 1])
siCount += 2
siNum += 2
Return
End If
sOutput.Add(siInput[siNum] & "-" & siInput[siCount])
Inc siCount
siNum = siCount
End If
 
End

Output:

0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39
-6, -3-1, 3-5, 7-11, 14, 15, 17-20

Go[edit]

package main
 
import (
"errors"
"fmt"
"strconv"
"strings"
)
 
func main() {
rf, err := rangeFormat([]int{
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39,
})
if err != nil {
fmt.Println(err)
return
}
fmt.Println("range format:", rf)
}
 
func rangeFormat(a []int) (string, error) {
if len(a) == 0 {
return "", nil
}
var parts []string
for n1 := 0; ; {
n2 := n1 + 1
for n2 < len(a) && a[n2] == a[n2-1]+1 {
n2++
}
s := strconv.Itoa(a[n1])
if n2 == n1+2 {
s += "," + strconv.Itoa(a[n2-1])
} else if n2 > n1+2 {
s += "-" + strconv.Itoa(a[n2-1])
}
parts = append(parts, s)
if n2 == len(a) {
break
}
if a[n2] == a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence repeats value %d", a[n2]))
}
if a[n2] < a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence not ordered: %d < %d", a[n2], a[n2-1]))
}
n1 = n2
}
return strings.Join(parts, ","), nil
}
Output:
range format: 0-2,4,6-8,11,12,14-25,27-33,35-39

Groovy[edit]

Ad Hoc Solution:

def range = { s, e -> s == e ? "${s}," : s == e - 1 ? "${s},${e}," : "${s}-${e}," }
 
def compressList = { list ->
def sb, start, end
(sb, start, end) = [''<<'', list[0], list[0]]
for (i in list[1..-1]) {
(sb, start, end) = i == end + 1 ? [sb, start, i] : [sb << range(start, end), i, i]
}
(sb << range(start, end))[0..-2].toString()
}
 
def compressRanges = { expanded -> compressList(Eval.me('[' + expanded + ']')) }

Test:

def s = '''
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
'''

println (compressRanges(s))
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Haskell[edit]

direct recursion[edit]

import Data.List (intercalate)
 
extractRange :: [Int] -> String
extractRange = intercalate "," . f
where f :: [Int] -> [String]
f (x1 : x2 : x3 : xs) | x1 + 1 == x2 && x2 + 1 == x3
= (show x1 ++ '-' : show xn) : f xs'
where (xn, xs'
) = g (x3 + 1) xs
g a (n : ns) | a == n = g (a + 1) ns
| otherwise = (a - 1, n : ns)
g a [] = (a - 1, [])
f (x : xs) = show x : f xs
f [] = []
> extractRange $ [0..2] ++ 4 : [6..8] ++ 11 : 12 : [14..25] ++ [27..33] ++ [35..39]
"0-2,4,6-8,11,12,14-25,27-33,35-39"

splitBy[edit]

We can, alternatively, define a reusable splitBy function, which returns a list of lists (split wherever the relationship between two consecutive items matches a supplied predicate function). Delegating to splitBy allows a reasonably clean definition of range formatting:

import Data.List (intercalate)
import Data.Function (on)
 
-- RANGE FORMAT --------------------------------------------------------------
 
rangeFormat :: [Int] -> String
rangeFormat = intercalate "," . (rangeString <$>) . splitBy ((/=) . succ)
where
rangeString xs
| length xs > 2 = x ++ '-' : last t
| otherwise = intercalate "," ps
where
ps@(x:t) = show <$> xs
 
 
-- GENERIC FUNCTION ----------------------------------------------------------
 
-- Split wherever a supplied predicate matches the relationship
-- between two consecutive items.
 
-- E.G. at boundaries between vowels and consonants:
-- splitBy (on (/=) (flip elem "aeiouAEIOU")) "Constantinople"
-- -> ["C","o","nst","a","nt","i","n","o","pl","e"]
 
-- At boundaries between non-successive integers:
-- splitBy ((/=) . succ) [0, 1, 2, 4, 6, 7, 8, 11, 12, 14]
-- -> [[0,1,2],[4],[6,7,8],[11,12],[14]]
 
splitBy :: (a -> a -> Bool) -> [a] -> [[a]]
splitBy _ [] = []
splitBy _ [x] = [[x]]
splitBy f xs@(_:t) = active : acc
where
(active, acc) =
foldr
(\(x, prev) (active, acc) ->
let current =
if null active
then [prev]
else active
in if f x prev
then ([x], current : acc)
else (x : current, acc))
([], [])
(zip xs t)
 
-- TEST ----------------------------------------------------------------------
main :: IO ()
main =
print $
rangeFormat
[ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]
Output:
"0-2,4,6-8,11,12,14-25,27-33,35-39"

chop[edit]

Or, we can pass a span-chopping function to Data.List.Split chop.

import Data.List (intercalate, groupBy, isPrefixOf)
import Data.List.Split (chop)
 
rangeFormat :: [Int] -> String
rangeFormat xs =
intercalate "," $
(\x -> head (if_ (length x > 1) (tail x) x)) <$>
groupBy isPrefixOf (rangeString <$> chop succSpan (zip xs (tail xs)))
where
rangeString [] = ""
rangeString xxs@(x:xs)
| null xs = show (snd x)
| otherwise = intercalate "-" (show <$> [fst x, snd (last xs)])
succSpan [] = ([], [])
succSpan (xxs@(x:xs))
| null ys = ([x], xs)
| otherwise = (ys, zs)
where
(ys, zs) = span (uncurry ((==) . succ)) xxs
 
if_ :: Bool -> a -> a -> a
if_ True x _ = x
if_ False _ y = y
 
main :: IO ()
main =
putStrLn $
rangeFormat [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 ]
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Icon and Unicon[edit]

procedure main()
 
R := [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 ]
 
write("Input list  := ",list2string(R))
write("Extracted sting := ",s := range_extract(R) | "FAILED")
end
 
procedure range_extract(R) #: return string/range representation of a list of unique integers
local s,sep,low,high,x
 
every if integer(x:= !R) ~= x then fail # ensure all are integers,
R := sort(set(R)) # unique, and sorted
 
s := sep := ""
while s ||:= sep || ( low := high := get(R) ) do { # lower bound of range
sep := ","
while high := ( R[1] = high + 1 ) do get(R) # find the end of range
if high > low+1 then s ||:= "-" || high # - record range of 3+
else if high = low+1 then push(R,high) # - range of 2, high becomes new low
}
return s
end
 
procedure list2string(L) #: helper to convert list to string
local s
 
every (s := "[ ") ||:= !L || " "
return s || "]"
end
Output:
Input list      := [ 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27
28 29 30 31 32 33 35 36 37 38 39 ]
Extracted sting := 0-2,4,6-8,11,12,14-25,27-33,35-39

J[edit]

Older versions of J will also need require 'strings'.

fmt=: [: ;@(8!:0) [`]`({. ; (',-' {~ 2 < #) ; {:)@.(2 <. #)
group=: <@fmt;.1~ 1 ~: 0 , 2 -~/\ ]
extractRange=: ',' joinstring group

Example use:

   extractRange 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
0-2,4,6-8,11,12,14-25,27-33,35-39

and

   extractRange (-6, 3, 2, 1), 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20
-6,-3-1,3-5,7-11,14,15,17-20

Other examples:

   extractRange i.101
0-100

The first 101 non-negative integers

 
extractRange (-. p:) i.101
0,1,4,6,8-10,12,14-16,18,20-22,24-28,30,32-36,38-40,42,44-46,48-52,54-58,60,62-66,68-70,72,74-78,80-82,84-88,90-96,98-100

Excluding those which are prime

 
extractRange 2}. (-. p:) i.101
4,6,8-10,12,14-16,18,20-22,24-28,30,32-36,38-40,42,44-46,48-52,54-58,60,62-66,68-70,72,74-78,80-82,84-88,90-96,98-100

Also excluding the first two non-negative integers (which are neither prime nor the product of non-empty lists of primes).

Java[edit]

public class RangeExtraction {
 
public static void main(String[] args) {
int[] arr = {0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39};
 
int len = arr.length;
int idx = 0, idx2 = 0;
while (idx < len) {
while (++idx2 < len && arr[idx2] - arr[idx2 - 1] == 1);
if (idx2 - idx > 2) {
System.out.printf("%s-%s,", arr[idx], arr[idx2 - 1]);
idx = idx2;
} else {
for (; idx < idx2; idx++)
System.out.printf("%s,", arr[idx]);
}
}
}
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39,

JavaScript[edit]

ES5[edit]

Imperative[edit]

function rangeExtraction(list) {
var len = list.length;
var out = [];
var i, j;
 
for (i = 0; i < len; i = j + 1) {
// beginning of range or single
out.push(list[i]);
 
// find end of range
for (var j = i + 1; j < len && list[j] == list[j-1] + 1; j++);
j--;
 
if (i == j) {
// single number
out.push(",");
} else if (i + 1 == j) {
// two numbers
out.push(",", list[j], ",");
} else {
// range
out.push("-", list[j], ",");
}
}
out.pop(); // remove trailing comma
return out.join("");
}
 
// using print function as supplied by Rhino standalone
print(rangeExtraction([
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
]));

Functional[edit]

Translation of: ES6
Translation of: Haskell
(function () {
'use strict';
 
// rangeFormat :: [Int] -> String
var rangeFormat = function (xs) {
return splitBy(function (a, b) {
return b - a > 1;
}, xs)
.map(rangeString)
.join(',');
};
 
// rangeString :: [Int] -> String
var rangeString = function (xs) {
return xs.length > 2 ? [head(xs), last(xs)].map(show)
.join('-') : xs.join(',');
};
 
// GENERIC FUNCTIONS
 
// Splitting not on a delimiter, but whenever the relationship between
// two consecutive items matches a supplied predicate function
 
// splitBy :: (a -> a -> Bool) -> [a] -> [[a]]
var splitBy = function (f, xs) {
if (xs.length < 2) return [xs];
var h = head(xs),
lstParts = xs.slice(1)
.reduce(function (a, x) {
var acc = a[0],
active = a[1],
prev = a[2];
 
return f(prev, x) ? (
[acc.concat([active]), [x], x]
) : [acc, active.concat(x), x];
}, [
[],
[h], h
]);
return lstParts[0].concat([lstParts[1]]);
};
 
// head :: [a] -> a
var head = function (xs) {
return xs.length ? xs[0] : undefined;
};
 
// last :: [a] -> a
var last = function (xs) {
return xs.length ? xs.slice(-1)[0] : undefined;
};
 
// show :: a -> String
var show = function (x) {
return JSON.stringify(x);
};
 
// TEST
return rangeFormat([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32,
33, 35, 36, 37, 38, 39
]);
})();
Output:
"0-2,4,6-8,11,12,14-25,27-33,35-39"

ES6[edit]

Translation of: Haskell

Defining the range format in terms of a reusable splitBy function:

(() => {
'use strict';
 
// rangeFormat :: [Int] -> String
const rangeFormat = xs =>
splitBy((a, b) => b - a > 1, xs)
.map(rangeString)
.join(',');
 
// rangeString :: [Int] -> String
const rangeString = xs =>
xs.length > 2 ? (
[head(xs), last(xs)].map(show)
.join('-')
) : xs.join(',')
 
 
// GENERIC FUNCTIONS
 
// Splitting not on a delimiter, but whenever the relationship between
// two consecutive items matches a supplied predicate function
 
// splitBy :: (a -> a -> Bool) -> [a] -> [[a]]
const splitBy = (f, xs) => {
if (xs.length < 2) return [xs];
const
h = head(xs),
lstParts = xs.slice(1)
.reduce(([acc, active, prev], x) =>
f(prev, x) ? (
[acc.concat([active]), [x], x]
) : [acc, active.concat(x), x], [
[],
[h],
h
]);
return lstParts[0].concat([lstParts[1]]);
};
 
// head :: [a] -> a
const head = xs => xs.length ? xs[0] : undefined;
 
// last :: [a] -> a
const last = xs => xs.length ? xs.slice(-1)[0] : undefined;
 
// show :: a -> String
const show = x => JSON.stringify(x);
 
// TEST
return rangeFormat([0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
]);
})();
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

jq[edit]

# Input should be an array
def extract:
reduce .[] as $i
# state is an array with integers or [start, end] ranges
([];
if length == 0 then [ $i ]
else ( .[-1]) as $last
| if ($last|type) == "array" then
if ($last[1] + 1) == $i then setpath([-1,1]; $i)
else . + [ $i ]
end
elif ($last + 1) == $i then setpath([-1]; [$last, $i])
else . + [ $i ]
end
end)
| map( if type == "number" then tostring
elif .[0] == .[1] -1
then "\(.[0]),\(.[1])" # satisfy special requirement
else "\(.[0])-\(.[1])" end )
| join(",") ;
Command and output:
$ jq -n -f extract_range.jq input.txt
"0-2,4,6-8,11,12,14-25,27-33,35-39"

Julia[edit]

This is perhaps an idiosyncratic solution. Numbers inside of runs are replaced with Xs, the list is converted into a comma separated string, and then Xs and extra commas are replaced with the range character via a regular expression.

 
function sprintfrange{T<:Integer}(a::Array{T,1})
len = length(a)
0 < len || return ""
dropme = falses(len)
dropme[2:end-1] = Bool[a[i-1]==a[i]-1 && a[i+1]==a[i]+1 for i in 2:(len-1)]
s = [string(i) for i in a]
s[dropme] = "X"
s = join(s, ",")
replace(s, r",[,X]+,", "-")
end
 
testa = [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]
 
println("Testing range-style formatting.")
println(" ", testa, "\n =>\n ", sprintfrange(testa))
 
Output:
   [0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39]
       =>
   0-2,4,6-8,11,12,14-25,27-33,35-39

K[edit]

grp : {(&~1=0,-':x)_ x}
fmt : {:[1=#s:$x;s;(*s),:[3>#s;",";"-"],*|s]}
erng: {{x,",",y}/,//'fmt'grp x}
Example:
  erng 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
"0-2,4,6-8,11,12,14-25,27-33,35-39"

Kotlin[edit]

// version 1.0.6
 
fun extractRange(list: List<Int>): String {
if (list.isEmpty()) return ""
val sb = StringBuilder()
var first = list[0]
var prev = first
 
fun append(index: Int) {
if (first == prev) sb.append(prev)
else if (first == prev - 1) sb.append(first, ",", prev)
else sb.append(first, "-", prev)
if (index < list.size - 1) sb.append(",")
}
 
for (i in 1 until list.size) {
if (list[i] == prev + 1) prev++
else {
append(i)
first = list[i]
prev = first
}
}
append(list.size - 1)
return sb.toString()
}
 
fun main(args: Array<String>) {
val list1 = listOf(-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20)
println(extractRange(list1))
println()
val list2 = listOf(0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39)
println(extractRange(list2))
}
Output:
-6,-3-1,3-5,7-11,14,15,17-20

0-2,4,6-8,11,12,14-25,27-33,35-39

Liberty BASIC[edit]

 
s$ = "0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24," + _
"25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39"
print ExtractRange$( s$)
end
 
function ExtractRange$( range$)
n = 1
count = ItemCount( range$, ",")
while n <= count
startValue = val( word$( range$, n, ","))
m = n + 1
while m <= count
nextValue = val( word$( range$, m, ","))
if nextValue - startValue <> m - n then exit while
m = m + 1
wend
if m - n > 2 then
ExtractRange$ = ExtractRange$ + str$( startValue) + "-" + str$( startValue + m - n - 1) + ","
else
for i = n to m - 1
ExtractRange$ = ExtractRange$ + str$( startValue + i - n) + ","
next i
end if
n = m
wend
ExtractRange$ = left$( ExtractRange$, len( ExtractRange$) - 1)
end function
 
function ItemCount( list$, separator$)
while word$( list$, ItemCount + 1, separator$) <> ""
ItemCount = ItemCount + 1
wend
end function
 
Output:
    0-2,4,6-8,11,12,14-25,27-33,35-39

LiveCode[edit]

Inefficient as it takes 2 passes

function rangeExtract nums
local prevNum, znums, rangedNums
set itemDelimiter to ", "
put the first item of nums into prevNum
repeat for each item n in nums
if n is (prevNum + 1) then
put n into prevNum
put "#" & n after znums
else
put n into prevNum
put return & n after znums
end if
end repeat
set itemDelimiter to "#"
repeat for each line z in znums
if z is empty then next repeat
switch the number of items of z
case 1
put z & "," after rangedNums
break
case 2
put item 1 of z & "," & item -1 of z & "," after rangedNums
break
default
put item 1 of z & "-" & item -1 of z & "," after rangedNums
end switch
end repeat
return char 1 to -2 of rangedNums --strip off trailing comma
end rangeExtract
 

Test

command testRangeExtract
local numbers
put "0, 1, 2, 4, 6, 7, 8, 11, 12, 14," \
&& "15, 16, 17, 18, 19, 20, 21, 22, 23, 24," \
&& "25, 27, 28, 29, 30, 31, 32, 33, 35, 36," \
&& "37, 38, 39" into numbers
put rangeExtract(numbers)
end testRangeExtract
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Lua[edit]

function extractRange (rList)
local rExpr, startVal = ""
for k, v in pairs(rList) do
if rList[k + 1] == v + 1 then
if not startVal then startVal = v end
else
if startVal then
if v == startVal + 1 then
rExpr = rExpr .. startVal .. "," .. v .. ","
else
rExpr = rExpr .. startVal .. "-" .. v .. ","
end
startVal = nil
else
rExpr = rExpr .. v .. ","
end
end
end
return rExpr:sub(1, -2)
end
 
local intList = {
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
}
print(extractRange(intList))
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Mathematica[edit]

 
rangeExtract[data_List] := ToString[Row[
Riffle[
Flatten[Split[Sort[data], #2 - #1 == 1 &] /. {a_Integer, __, b_} :> Row[{a, "-", b}]],
","]
]];
 

Example:

rangeExtract[{0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39}]

"0-2,4,6-8,11,12,14-25,27-33,35-39"

MATLAB / Octave[edit]

function S=range_extraction(L)
% Range extraction
L(end+1) = NaN;
S = int2str(L(1));
k = 1;
while (k < length(L)-1)
if (L(k)+1==L(k+1) && L(k)+2==L(k+2) )
m = 2;
while (L(k)+m==L(k+m))
m = m+1;
end
k = k+m-1;
S = [S,'-',int2str(L(k))];
else
k = k+1;
S = [S,',',int2str(L(k))];
end
end
end
 
disp(range_extraction([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, ...
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, ...
28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]))
Output (Octave):
0-2,4,6-8,11,12,14-25,27-33,35-39

MUMPS[edit]

RANGCONT(X) ;Integer range contraction
NEW Y,I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ SET Y="",SEQ=0,PREV="",CONT=0
FOR I=1:1:$LENGTH(X,",") DO
.SET NOTFIRST=$LENGTH(Y),CURR=$PIECE(X,",",I),NEXT=$PIECE(X,",",I+1)
.FOR Q:$EXTRACT(CURR)'=" " S CURR=$EXTRACT(CURR,2,$LENGTH(CURR))  ;clean up leading spaces
.S SEQ=((CURR-1)=PREV)&((CURR+1)=NEXT)
.IF 'NOTFIRST SET Y=CURR
.IF NOTFIRST DO
..;Order matters due to flags
..IF CONT&SEQ ;Do nothing
..IF 'CONT&'SEQ SET Y=Y_","_CURR
..IF CONT&'SEQ SET Y=Y_CURR,CONT=0
..IF 'CONT&SEQ SET Y=Y_"-",CONT=1
.SET PREV=CURR
IF CONT SET Y=Y_PREV
K I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ
QUIT Y

Example:

USER>SET S="0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39"
 
USER>W $$RANGCONT^ROSETTA(S)
0-2,4,6-8,11,12,14-25,27-33,35-39

NetRexx[edit]

NetRexx Ver. 1[edit]

/*NetRexx program to test range extraction. ***************************
* 07.08.2012 Walter Pachl derived from my Rexx Version
* Changes: line continuation in aaa assignment changed
* 1e99 -> 999999999
* Do -> Loop
* words(aaa) -> aaa.words()
* word(aaa,i) -> aaa.word(i)
**********************************************************************/

Say 'NetRexx program derived from Rexx'
aaa='0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29'
aaa=aaa' 30 31 32 33 35 36 37 38 39'
say 'old='aaa;
aaa=aaa 999999999 /* artificial number at the end */
i=0 /* initialize index */
ol='' /* initialize output string */
comma='' /* will become a ',' lateron */
inrange=0
Loop While i<=aaa.words /* loop for all numbers */
i=i+1 /* index of next number */
n=aaa.word(i) /* the now current number */
If n=999999999 Then Leave /* we are at the end */
If inrange Then Do /* range was opened */
If aaa.word(i+1)<>n+1 Then Do /* following word not in range */
ol=ol||n /* so this number is the end */
inrange=0 /* and the range is over */
End /* else ignore current number */
End
Else Do /* not in a range */
ol=ol||comma||n /* add number (with comma) */
comma=',' /* to the output string */
If aaa.word(i+2)=n+2 Then Do /* if the nr after the next fits */
inrange=1 /* open a range */
ol=ol'-' /* append the range connector */
End
End
End
Say 'new='ol
Output:
NetRexx program derived from Rexx
old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
new=0-2,4,6-8,11,12,14-25,27-33,35-39                   

NetRexx Ver. 2[edit]

Translation of: Java
/* NetRexx */
options replace format comments java crossref symbols nobinary
 
runSample(arg)
return
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- Compact a list of numbers by reducing ranges
method compact(expanded) public static
nums = expanded.changestr(',', ' ').space -- remove possible commas & clean up the string
rezult = ''
 
RANGE = 0
FIRST = nums.word(1) -- set starting value
loop i_ = 2 to nums.words -- each word in the string is a number to examine
LOCAL = nums.word(i_)
if LOCAL - FIRST - RANGE == 1 then do
-- inside a range
RANGE = RANGE + 1
end
else do
-- not inside a range
if RANGE \= 0 then do
-- we have a range of numbers so collect this and reset
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE || ','
RANGE = 0
end
else do
-- just collect this number
rezult = rezult || FIRST || ','
end
FIRST = LOCAL -- bump new starting value
end
end i_
 
if RANGE \= 0 then do
-- terminating value is a range
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE
end
else do
-- terminating value is a single number
rezult = rezult || FIRST
end
 
return rezult.space(1, ',') -- format and return result string
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- determine if the range delimiter should be a comma or dash
method delim(range) private static
if range == 1 then dlm = ','
else dlm = '-'
return dlm
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- sample driver
method runSample(arg) public static
 
parse arg userInput
td = 0
if userInput.words > 0 then do
-- use input from command line
td[0] = td[0] + 1; r_ = td[0]; td[r_] = userInput
end
else do
-- use canned test data
td[0] = td[0] + 1; r_ = td[0]; td[r_] = ' -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20'
td[0] = td[0] + 1; r_ = td[0]; td[r_] = ' 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
td[0] = td[0] + 1; r_ = td[0]; td[r_] = ' -4, -3, -2, 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
end
 
loop r_ = 1 to td[0]
say 'Original: ' td[r_].changestr(',', ' ').space(1, ',')
say 'Compacted:' compact(td[r_])
say
end r_
return
 
Output:
Original:  -6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20
Compacted: -6,-3-1,3-5,7-11,14,15,17-20

Original:  0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: 0-2,4,6-8,11,12,14-25,27-33,35-39

Original:  -4,-3,-2,0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: -4--2,0-2,4,6-8,11,12,14-25,27-33,35-39

Nim[edit]

import parseutils, re, strutils
 
proc extractRange(input: string): string =
var list = input.replace(re"\s+").split(',').map(parseInt)
var ranges: seq[string] = @[]
var i = 0
while i < list.len:
var first = list[i] # first element in the current range
var offset = i
while True: # skip ahead to the end of the current range
if i + 1 >= list.len:
# reached end of the list
break
if list[i + 1] - (i + 1) != first - offset:
# next element isn't in the current range
break
i.inc
var last = list[i] # last element in the current range
case last - first
of 0: ranges.add($first)
of 1: ranges.add("$1,$2".format([$first, $last]))
else: ranges.add("$1-$2".format([$first, $last]))
i.inc
return ranges.join(",")
 
echo("""
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39""".extractRange)
Output:
0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39

Objeck[edit]

Translation of: Java
class IdentityMatrix {
function : Main(args : String[]) ~ Nil {
Compress2Range("-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20")->PrintLine();
 
Compress2Range("0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39")->PrintLine();
}
 
function : Compress2Range(expanded : String) ~ String {
result := "";
nums := expanded->ReplaceAll(" ", "")->Split(",");
firstNum := nums[0]->ToInt();
rangeSize := 0;
for(i:= 1; i < nums->Size(); i += 1;) {
thisNum := nums[i]->ToInt();
if(thisNum - firstNum - rangeSize = 1) {
rangeSize += 1;
}
else{
if(rangeSize <> 0){
result->Append(firstNum);
result->Append((rangeSize = 1) ? ",": "-");
result->Append(firstNum+rangeSize);
result->Append(",");
rangeSize := 0;
}
else {
result->Append(firstNum);
result->Append(",");
};
firstNum := thisNum;
};
};
 
if(rangeSize <> 0){
result->Append(firstNum);
result->Append((rangeSize = 1) ? "," : "-");
result->Append(firstNum + rangeSize);
rangeSize := 0;
}
else {
result->Append(firstNum);
};
 
return result;
}
}
 

Oberon-2[edit]

Oxford Oberon-2

 
MODULE RangeExtraction;
IMPORT Out;
 
PROCEDURE Range(s: ARRAY OF INTEGER);
VAR
i,j: INTEGER;
 
PROCEDURE Emit(sep: CHAR);
BEGIN
IF i > 2 THEN
Out.Int(s[j],3);Out.Char('-');Out.Int(s[j + i - 1],3);Out.Char(sep);
INC(j,i)
ELSE
Out.Int(s[j],3);Out.Char(sep);
INC(j)
END;
END Emit;
 
BEGIN
j := 0;i := -1;
LOOP
INC(i);
IF j + i >= LEN(s) THEN
Emit(0AX);
EXIT
ELSIF s[j + i] # (s[j] + i) THEN
Emit(',');
i := 0;
END
END
END Range;
 
VAR
seq0: ARRAY 33 OF INTEGER;
seq1: ARRAY 20 OF INTEGER;
BEGIN
seq0[0] := 0;
seq0[1] := 1;
seq0[2] := 2;
seq0[3] := 4;
seq0[4] := 6;
seq0[5] := 7;
seq0[6] := 8;
seq0[7] := 11;
seq0[8] := 12;
seq0[9] := 14;
seq0[10] := 15;
seq0[11] := 16;
seq0[12] := 17;
seq0[13] := 18;
seq0[14] := 19;
seq0[15] := 20;
seq0[16] := 21;
seq0[17] := 22;
seq0[18] := 23;
seq0[19] := 24;
seq0[20] := 25;
seq0[21] := 27;
seq0[22] := 28;
seq0[23] := 29;
seq0[24] := 30;
seq0[25] := 31;
seq0[26] := 32;
seq0[27] := 33;
seq0[28] := 35;
seq0[29] := 36;
seq0[30] := 37;
seq0[31] := 38;
seq0[32] := 39;
Range(seq0);
seq1[0] := -6;
seq1[1] := -3;
seq1[2] := -2;
seq1[3] := -1;
seq1[4] := 0;
seq1[5] := 1;
seq1[6] := 3;
seq1[7] := 4;
seq1[8] := 5;
seq1[9] := 7;
seq1[10] := 8;
seq1[11] := 9;
seq1[12] := 10;
seq1[13] := 11;
seq1[14] := 14;
seq1[15] := 15;
seq1[16] := 17;
seq1[17] := 18;
seq1[18] := 19;
seq1[19] := 20;
Range(seq1)
END RangeExtraction.
 
Output:
  0-  2,  4,  6-  8, 11, 12, 14- 25, 27- 33, 35- 39
 -6, -3-  1,  3-  5,  7- 11, 14, 15, 17- 20

Objective-C[edit]

We can use NSIndexSet to do this. However, it only works for non-negative integers.

Works with: Mac OS X version 10.7+
Works with: iOS version 5+
#import <Foundation/Foundation.h>
 
NSString *extractRanges(NSArray *nums) {
NSMutableIndexSet *indexSet = [[NSMutableIndexSet alloc] init];
for (NSNumber *n in nums) {
if ([n integerValue] < 0)
@throw [NSException exceptionWithName:NSInvalidArgumentException reason:@"negative number not supported" userInfo:nil];
[indexSet addIndex:[n unsignedIntegerValue]];
}
NSMutableString *s = [[NSMutableString alloc] init];
[indexSet enumerateRangesUsingBlock:^(NSRange range, BOOL *stop) {
if (s.length)
[s appendString:@","];
if (range.length == 1)
[s appendFormat:@"%lu", range.location];
else if (range.length == 2)
[s appendFormat:@"%lu,%lu", range.location, range.location+1];
else
[s appendFormat:@"%lu-%lu", range.location, range.location+range.length-1];
}];
return s;
}
 
int main() {
@autoreleasepool {
 
NSLog(@"%@", extractRanges(@[@0, @1, @2, @4, @6, @7, @8, @11, @12, @14,
@15, @16, @17, @18, @19, @20, @21, @22, @23, @24,
@25, @27, @28, @29, @30, @31, @32, @33, @35, @36,
@37, @38, @39]));
 
}
return 0;
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

OCaml[edit]

let range_extract = function
| [] -> []
| x::xs ->
let f (i,j,ret) k =
if k = succ j then (i,k,ret) else (k,k,(i,j)::ret) in
let (m,n,ret) = List.fold_left f (x,x,[]) xs in
List.rev ((m,n)::ret)
 
let string_of_range rng =
let str (a,b) =
if a = b then string_of_int a
else Printf.sprintf "%d%c%d" a (if b = succ a then ',' else '-') b in
String.concat "," (List.map str rng)
 
let () =
let li =
[ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;
22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ]
in
let rng = range_extract li in
print_endline(string_of_range rng)
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

ooRexx[edit]

Translation of: NetRexx Ver. 2
Translation of: Java
/* Rexx */
 
parse arg userInput
call runSample userInput
return
exit
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- Compact a list of numbers by reducing ranges
compact:
procedure
--trace ?r;nop
parse arg expanded
nums = expanded~changestr(',', ' ')~space -- remove possible commas & clean up the string
rezult = ''
 
RANGE = 0
FIRST = nums~word(1) -- set starting value
loop i_ = 2 to nums~words -- each word in the string is a number to examine
LOCAL = nums~word(i_)
if LOCAL - FIRST - RANGE == 1 then do
-- inside a range
RANGE += 1
end
else do
-- not inside a range
if RANGE \= 0 then do
-- we have a range of numbers so collect this and reset
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE || ','
RANGE = 0
end
else do
-- just collect this number
rezult = rezult || FIRST || ','
end
FIRST = LOCAL -- bump new starting value
end
end i_
if RANGE \= 0 then do
-- collect terminating value (a range)
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE
end
else do
-- collect terminating value (a single number)
rezult = rezult || FIRST
end
 
return rezult~space(1, ',') -- format and return result string
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- determine if the range delimiter should be a comma or dash
delim:
procedure
parse arg range .
if range == 1 then dlm = ','
else dlm = '-'
return dlm
 
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
-- sample driver
runSample:
procedure
parse arg userInput
td. = 0
if userInput~words > 0 then do
td.0 += 1; r_ = td.0; td.r_ = userInput
end
else do
td.0 += 1; r_ = td.0; td.r_ = '-6 -3 -2 -1 0 1 3 4 5 7 8 9 10 11 14 15 17 18 19 20'
td.0 += 1; r_ = td.0; td.r_ = '0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
td.0 += 1; r_ = td.0; td.r_ = '-4, -3, -2, 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
end
 
loop r_ = 1 to td.0
say 'Original: ' td.r_~changestr(',', ' ')~space(1, ',')
say 'Compacted:' compact(td.r_)
say
end r_
return
 
Output:
Original:  -6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20
Compacted: -6,-3-1,3-5,7-11,14,15,17-20

Original:  0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: 0-2,4,6-8,11,12,14-25,27-33,35-39

Original:  -4,-3,-2,0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: -4--2,0-2,4,6-8,11,12,14-25,27-33,35-39

OxygenBasic[edit]

This example does not show the output mentioned in the task description on this page (or a page linked to from here). Please ensure that it meets all task requirements and remove this message.
Note that phrases in task descriptions such as "print and display" and "print and show" for example, indicate that (reasonable length) output be a part of a language's solution.


 
dim sys ints(100)
ints=>
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
 
function ShowRange(sys*i) as string
'==================================
pr=""
n=0
e=0
j=0
k=-1
do
j++
n=i(j)
e=i(j+1)
if e<j then
exit do
end if
if e=n+1 and i(j+2)=n+2 then 'LOOKAHEAD
if k=-1 then k=n
else
if k>=0 then
pr+=k "-" i(j+1) ", " 'RANGE OF VALUES
j++
k=-1
else
pr+=n ", " 'SINGLE VALUES
end if
end if
end do
return left pr, len(pr)-2
end function
 
 
print ShowRange ints
 

Oz[edit]

declare
fun {Extract Xs}
{CommaSeparated
{Map {ExtractRanges Xs} RangeToString}}
end
 
fun {ExtractRanges Xs}
fun {Loop Ys Start End}
case Ys
of Y|Yr andthen Y == End+1 then {Loop Yr Start Y}
[] Y|Yr then Start#End|{Loop Yr Y Y}
[] nil then [Start#End]
end
end
in
case Xs
of X|Xr then {Loop Xr X X}
[] nil then nil
end
end
 
fun {RangeToString S#E}
if E-S >= 2 then
{VirtualString.toString S#"-"#E}
else
{CommaSeparated
{Map {List.number S E 1} Int.toString}}
end
end
 
fun {CommaSeparated Xs}
{Flatten {Intersperse "," Xs}}
end
 
fun {Intersperse Sep Xs}
case Xs of X|Y|Xr then
X|Sep|{Intersperse Sep Y|Xr}
else
Xs
end
end
in
{System.showInfo
{Extract [ 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39 ]}}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Pascal[edit]

Works with: Free Pascal version 2.6.2
program RangeExtraction;
 
{$mode objfpc}{$H+}
 
uses
{$IFDEF UNIX}{$IFDEF UseCThreads}
cthreads,
{$ENDIF}{$ENDIF}
SysUtils;
 
function RangeExtraction(const Seq: array of integer): String;
const
SubSeqLen = 3; // minimal length of the range, can be changed.
var
i, j: Integer;
Separator: string = '';
begin
Result := '';
i := Low(Seq);
while i <= High(Seq) do
begin
j := i;
// All subsequent values, starting from i, up to High(Seq) possibly
while ((j < High(Seq)) and ((Seq[j+1]-Seq[j]) = 1)) do
Inc(j);
// is it a range ?
if ((j-i) >= (SubSeqLen-1)) then
begin
Result := Result + Format(Separator+'%d-%d',[Seq[i],Seq[j]]);
i := j+1; // Next value to be processed
Separator := ',';
end
else
begin
// Loop, to process the case SubSeqLen > 3
while i<=j do
begin
Result := Result + Format(Separator+'%d',[Seq[i]]);
Inc(i); // Next value to be processed
Separator := ',';
end;
end;
end;
End;
 
procedure DisplayRange(const Seq: array of integer);
var
i: Integer;
begin
Write(Format('[%d', [Seq[Low(Seq)]]));
for i := Low(Seq) + 1 to High(Seq) do
Write(Format(',%d', [Seq[i]]));
WriteLn('] => ' + RangeExtraction(Seq));
WriteLn;
End;
 
begin
DisplayRange([0]);
DisplayRange([0,1]);
DisplayRange([0,2]);
DisplayRange([0,1,2]);
DisplayRange([0,1,2,3]);
DisplayRange([0,1,2,3,4,5,6,7]);
DisplayRange([0,2,3,4,5,6,7,9]);
DisplayRange([0,2,4,6,8,10]);
DisplayRange([0,1,2,3,4,5,6,7,9]);
DisplayRange([0,1,2,3,4,6,9,10,11,12]);
 
DisplayRange([
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]);
ReadLn;
end.
 
Output:
[0] => 0

[0,1] => 0,1

[0,2] => 0,2

[0,1,2] => 0-2

[0,1,2,3] => 0-3

[0,1,2,3,4,5,6,7] => 0-7

[0,2,3,4,5,6,7,9] => 0,2-7,9

[0,2,4,6,8,10] => 0,2,4,6,8,10

[0,1,2,3,4,5,6,7,9] => 0-7,9

[0,1,2,3,4,6,9,10,11,12] => 0-4,6,9-12

[0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35
,36,37,38,39] => 0-2,4,6-8,11,12,14-25,27-33,35-39

Perl[edit]

Using regexes. Also handles +/- and negative integer ranges.

sub rangext {
my $str = join ' ', @_;
1 while $str =~ s{([+-]?\d+) ([+-]?\d+)}
{$1.(abs($2 - $1) == 1 ? '~' : ',').$2}eg; # abs for neg ranges
$str =~ s/(\d+)~(?:[+-]?\d+~)+([+-]?\d+)/$1-$2/g;
$str =~ tr/~/,/;
return $str;
}
 
# Test and display
my @test = qw(0 1 2 4 6 7 8 11 12 14,
15 16 17 18 19 20 21 22 23 24,
25 27 28 29 30 31 32 33 35 36,
37 38 39);
print rangext(@test), "\n";
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39
Library: Set::IntSpan
use Set::IntSpan;
sub rangext { return Set::IntSpan->new(@_) . '' } # stringized
use Set::IntSpan::Fast;
sub rangext { return Set::IntSpan::Fast->new(@_)->as_string }

Set::IntSpan and Set::IntSpan::Fast are similar. "Fast" does a binary search for member testing (not part of the task here). Both accept negatives.

Perl 6[edit]

sub range-extraction (*@ints) {
my $prev = NaN;
my @ranges;
 
for @ints -> $int {
if $int == $prev + 1 {
@ranges[*-1].push: $int;
}
else {
@ranges.push: [$int];
}
$prev = $int;
}
join ',', @ranges.map: -> @r { @r > 2 ?? "@r[0][email protected][*-1]" !! @r }
}
 
say range-extraction
-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20;
 
say range-extraction
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39;
Output:
-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39

Phix[edit]

function spout(integer first, integer this, sequence s)
string res
if first=this-1 then
res = sprintf("%d",s[first])
else
res = sprintf("%d%s%d",{s[first],iff(first=this-2?',':'-'),s[this-1]})
end if
return res
end function
 
function extract_ranges(sequence s)
integer first = 1
string out = ""
if length(s)!=0 then
for i=2 to length(s) do
if s[i]!=s[i-1]+1 then
out &= spout(first,i,s)&','
first = i
end if
end for
out &= spout(first,length(s)+1,s)
end if
return out
end function
 
puts(1,extract_ranges({0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39}))
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

PicoLisp[edit]

(de rangeextract (Lst)
(glue ","
(make
(while Lst
(let (N (pop 'Lst) M N)
(while (= (inc M) (car Lst))
(setq M (pop 'Lst)) )
(cond
((= N M) (link N))
((= (inc N) M) (link N M))
(T (link (list N '- M))) ) ) ) ) ) )
Output:
: (rangeextract
   (0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22
      23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 ) )

-> "0-2,4,6-8,11,12,14-25,27-33,35-39"

PL/I[edit]

/* Modified 19 November 2011 to meet requirement that there be at  */
/* least 3 items in a run. */
range_extraction: /* 17 August 2010 */
procedure options (main);
declare (c, d) character (1);
declare (old, new, initial) fixed binary (31);
declare in file;
declare out file output;
 
open file (in) title ('/range2.dat,type(text),recsize(80)' );
open file (out) output title ('/range2.out,type(text),recsize(70)');
 
c = ' '; d = ',';
get file (in) list (old);
do forever;
initial = old;
on endfile (in) begin;
put file (out) edit (c, trim(old)) (a);
stop;
end;
get file (in) list (new);
if new = old+1 then
do; /* we have a run. */
on endfile (in) begin;
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
stop;
end;
do while (new = old+1);
old = new;
get file (in) list (new);
end;
/* At this point, old holds the last in a run; */
/* initial holds the first in a run. */
/* if there are only two members in a run, don't use the */
/* range notation. */
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
old = new;
end;
else /* we have an isolated value. */
do;
put file (out) edit (c, trim(old)) (a);
old = new;
end;
c, d = ',';
end;
end range_extraction;

OUTPUT 17/8/2010:

 
0-2,4,6-8,11-12,14-25,27-33,35-39
 
Output:
 0-2,4,6-8,11,12,14-25,27-33,35-39

PowerShell[edit]

 
function range-extraction($arr) {
if($arr.Count -gt 2) {
$a, $b, $c, $arr = $arr
$d = $e = $c
if((($a + 1) -eq $b) -and (($b + 1) -eq $c)) {
$test = $true
while($arr -and $test) {
$d = $e
$e, $arr = $arr
$test = ($d+1) -eq $e
}
if($test){"$a-$e"}
elseif((-not $arr) -and $test){"$a-$d"}
elseif(-not $arr){"$a-$d,$e"}
else{"$a-$d," + (range-extraction (@($e)+$arr))}
}
elseif(($b + 1) -eq $c) {"$a," + (range-extraction (@($b, $c)+$arr))}
else {"$a,$b," + (range-extraction (@($c)+$arr))}
} else {
switch($arr.Count) {
0 {""}
1 {"$arr"}
2 {"$($arr[0]),$($arr[1])"}
}
}
}
range-extraction @(0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39)
 

Output:

0-2,4,6-8,11,12,14-25,27-33,35-39

Prolog[edit]

Works with SWI-Prolog and library clpfd.
The code uses three predicates extract_Range/2, study_Range/2 and pack_Range/2.
Every predicate works in both directions arg1 towards arg2 and arg2 towards arg1, so that Range extraction and Range expansion work with the same predicates but in reverse order.

range_extract :-
L = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39] ,
writeln(L),
pack_Range(L, LP),
maplist(study_Range, R, LP),
extract_Range(LA, R),
atom_chars(A, LA),
writeln(A).
 
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% extract_Range(?In, ?Out)
% In  : '-6,-3--1,3-5,7-11,14,15,17-20' =>
% Out : [-6], [-3--1], [3-5],[7-11], [14],[15], [17-20]
%
extract_Range([], []).
 
 
extract_Range(X , [Range | Y1]) :-
get_Range(X, U-U, Range, X1),
extract_Range(X1, Y1).
 
 
 
get_Range([], Range-[], Range, []).
get_Range([','|B], Range-[], Range, B) :- !.
 
get_Range([A | B], EC, Range, R) :-
append_dl(EC, [A | U]-U, NEC),
get_Range(B, NEC, Range, R).
 
 
append_dl(X-Y, Y-Z, X-Z).
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% study Range(?In, ?Out)
% In  : [-6]
% Out : [-6,-6]
%
% In  : [-3--1]
% Out : [-3, -1]
%
study_Range(Range1, [Deb, Deb]) :-
catch(number_chars(Deb, Range1), Deb, false).
 
study_Range(Range1, [Deb, Fin]) :-
append(A, ['-'|B], Range1),
A \= [],
number_chars(Deb, A),
number_chars(Fin, B).
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
:- use_module(library(clpfd)).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Pack Range(?In, ?Out)
% In  : -6,
% Out : [-6]
%
% In  : -3, -2,-1
% Out : [-3,-1]
%
pack_Range([],[]).
 
pack_Range([X|Rest],[[X | V]|Packed]):-
run(X,Rest, [X|V], RRest),
pack_Range(RRest,Packed).
 
 
 
run(Fin,[Other|RRest], [Deb, Fin],[Other|RRest]):-
Fin #\= Deb,
Fin #\= Deb + 1,
Other #\= Fin+1.
 
run(Fin,[],[_Var, Fin],[]).
 
run(Var,[Var1|LRest],[Deb, Fin], RRest):-
Fin #\= Deb,
Fin #\= Deb + 1,
Var1 #= Var + 1,
run(Var1,LRest,[Deb, Fin], RRest).
 
run(Val,[Other|RRest], [Val, Val],[Other|RRest]).
 
Output:
?- range_extract.
[0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39]
0-2,4,6-8,11,12,14-25,27-33,35-39
true

PureBasic[edit]

Even though the example integer list only includes ascending ranges this code will also handles descending ranges.

DataSection
Data.i 33 ;count of elements to be read
Data.i 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Data.i 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
EndDataSection
 
NewList values()
;setup list
Define elementCount, i
Read.i elementCount
For i = 1 To elementCount
AddElement(values()): Read.i values()
Next
 
Procedure.s rangeExtract(List values())
Protected listSize = ListSize(values()) - 1
Protected rangeMarker, rangeStart, rangeIncrement, retraceSteps, rangeSize, endOfRange, output.s, sub.s
 
ForEach values()
rangeStart = values():
sub = Str(rangeStart)
If NextElement(values())
retraceSteps = 1
rangeIncrement = values() - rangeStart
If rangeIncrement = 1 Or rangeIncrement = -1
;found start of possible range
If ListIndex(values()) <> listSize
retraceSteps = 2
rangeSize = 2
endOfRange = #False
rangeMarker = values()
While NextElement(values())
If values() - rangeMarker <> rangeIncrement
endOfRange = #True
Break
EndIf
rangeSize + 1
rangeMarker = values()
Wend
 
If rangeSize > 2
sub = Str(rangeStart) + "-" + Str(rangeMarker)
If Not endOfRange
retraceSteps = 0 ;at end of list
Else
retraceSteps = 1
EndIf
EndIf
EndIf
EndIf
 
;return to the value before look-aheads
While retraceSteps > 0
PreviousElement(values()): retraceSteps - 1
Wend
EndIf
 
output + sub + ","
Next
 
ProcedureReturn RTrim(output, ",")
EndProcedure
 
If OpenConsole()
PrintN(rangeExtract(values()))
 
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
Input()
CloseConsole()
EndIf
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Python[edit]

def range_extract(lst):
'Yield 2-tuple ranges or 1-tuple single elements from list of increasing ints'
lenlst = len(lst)
i = 0
while i< lenlst:
low = lst[i]
while i <lenlst-1 and lst[i]+1 == lst[i+1]: i +=1
hi = lst[i]
if hi - low >= 2:
yield (low, hi)
elif hi - low == 1:
yield (low,)
yield (hi,)
else:
yield (low,)
i += 1
 
def printr(ranges):
print( ','.join( (('%i-%i' % r) if len(r) == 2 else '%i' % r)
for r in ranges ) )
 
if __name__ == '__main__':
for lst in [[-8, -7, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7,
8, 9, 10, 11, 14, 15, 17, 18, 19, 20],
[0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]]:
#print(list(range_extract(lst)))
printr(range_extract(lst))
Output:
-8--6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39
Output:
if the printr(...) statement is commented-out instead of the print(...) statement directly above it.

This shows the tuples yielded by generator function range_extract.

[(-8, -6), (-3, 1), (3, 5), (7, 11), (14,), (15,), (17, 20)]
[(0, 2), (4,), (6, 8), (11,), (12,), (14, 25), (27, 33), (35, 39)]

Qi[edit]

 
(define make-range
Start Start -> ["," Start]
Start End -> ["," Start "," End] where (= End (+ Start 1))
Start End -> ["," Start "-" End])
 
(define range-extract-0
Start End [] -> (make-range Start End)
Start End [A|As] -> (range-extract-0 Start A As) where (= (+ 1 End) A)
Start End [A|As] -> (append (make-range Start End) (range-extract-0 A A As)))
 
(define range-extract
[A |As] -> (FORMAT NIL "~{~a~}" (tail (range-extract-0 A A As))))
 
(range-extract [ 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39])
 
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

R[edit]

extract.range = function(v)
{r = c(1, which(diff(v) != 1) + 1, length(v) + 1)
# 'r' holds the index of the start of each run of sequential
# elements.
paste0(collapse = ",", v[head(r, -1)], ifelse(diff(r) == 1, "",
paste0(
ifelse(diff(r) == 2, ",", "-"),
v[r[-1] - 1])))}
 
print(extract.range(c(
-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20)))
print(extract.range(c(
0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)))

Racket[edit]

 
#lang racket
 
(define (list->ranges xs)
(define (R lo hi)
(if (= lo hi) (~a lo) (~a lo (if (= 1 (- hi lo)) "," "-") hi)))
(let loop ([xs xs] [lo #f] [hi #f] [r '()])
(cond [(null? xs) (string-join (reverse (if lo (cons (R lo hi) r) r)) ",")]
[(not hi) (loop (cdr xs) (car xs) (car xs) r)]
[(= 1 (- (car xs) hi)) (loop (cdr xs) lo (car xs) r)]
[else (loop xs #f #f (cons (R lo hi) r))])))
 
(list->ranges '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23
24 25 27 28 29 30 31 32 33 35 36 37 38 39))
;; -> "0-2,4,6-8,11,12,14-25,27-33,35-39"
 

REXX[edit]

Note that the two numbers   11   and   12   are not considered a range.

version 1[edit]

This REXX version isn't limited to integers.

/*REXX program creates a  range extraction  from a  list of numbers  (can be negative.) */
old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
#=words(old) /*number of integers in the number list*/
new= /*the new list, possibly with ranges. */
do j=1 to #; x=word(old,j) /*obtain Jth number in the old list. */
new=new',' x /*append " " to " new " */
inc=1 /*start with an increment of one (1). */
do k=j+1 to #; y=word(old,k) /*get the Kth number in the number list*/
if y\==x+inc then leave /*is this number not > previous by inc?*/
inc=inc+1; g=y /*increase the range, assign G (good).*/
end /*k*/
if k-1=j | g=x+1 then iterate /*Is the range=0│1? Then keep truckin'*/
new=new'-'g; j=k-1 /*indicate a range of #s; change index*/
end /*j*/
 
new=space(substr(new, 2), 0) /*elide leading comma, also all blanks.*/
say 'old:' old /*display the old range of numbers. */
say 'new:' new /* " " new list " " */
/*stick a fork in it, we're all done. */

output   when using the (internal) list of numbers:

old: 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
new: 0-2,4,6-8,11,12,14-25,27-33,35-39

version 1a[edit]

The REXX version is the same as above, but doesn't modify a   do   loop's index   (j).

/*REXX program creates a  range extraction  from a  list of numbers  (can be negative.) */
old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
#=words(old); j=0 /*number of integers in the number list*/
new= /*the new list, possibly with ranges. */
do while j<#; j=j+1; x=word(old,j) /*get the Jth number in the number list*/
new=new',' x /*append " " to " new " */
inc=1 /*start with an increment of one (1). */
do k=j+1 to #; y=word(old,k) /*get the Kth number in the number list*/
if y\==x+inc then leave /*is this number not > previous by inc?*/
inc=inc+1; g=y /*increase the range, assign G (good).*/
end /*k*/
if k-1=j | g=x+1 then iterate /*Is the range=0│1? Then keep truckin'*/
new=new'-'g; j=k-1 /*indicate a range of numbers; change J*/
end /*while*/
 
new=space(substr(new, 2), 0) /*elide leading comma, also all blanks.*/
say 'old:' old /*display the old range of numbers. */
say 'new:' new /* " " new list " " */
/*stick a fork in it, we're all done. */

output   is the same as the 1st REXX version.

version 2[edit]

Somewhat simplified !?!

/*REXX program to test range extraction. ******************************
* 07.08.2012 Walter Pachl
**********************************************************************/

aaa='0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29',
'30 31 32 33 35 36 37 38 39'
say 'old='aaa;
aaa=aaa 1e99 /* artificial number at the end */
i=0 /* initialize index */
ol='' /* initialize output string */
comma='' /* will become a ',' lateron */
inrange=0
Do While i<=words(aaa) /* loop for all numbers */
i=i+1 /* index of next number */
n=word(aaa,i) /* the now current number */
If n=1e99 Then Leave /* we are at the end */
If inrange Then Do /* range was opened */
If word(aaa,i+1)<>n+1 Then Do /* following word not in range */
ol=ol||n /* so this number is the end */
inrange=0 /* and the range is over */
End /* else ignore current number */
End
Else Do /* not in a range */
ol=ol||comma||n /* add number (with comma) */
comma=',' /* to the output string */
If word(aaa,i+2)=n+2 Then Do /* if the nr after the next fits */
inrange=1 /* open a range */
ol=ol'-' /* append the range connector */
End
End
End
Say 'new='ol
 

Output is the same as above.


This example is incomplete. Does not show output from required task example Please ensure that it meets all task requirements and remove this message.

Ring[edit]

 
# Project : Range extraction
# Date  : 2017/11/08
# Author : Gal Zsolt [~ CalmoSoft ~]
# Email  : <[email protected]>
 
int = "-6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20"
int = str2list(substr(int, ",", nl))
sumint = []
intnew = 1
for n=1 to len(int)
flag = 0
nr = 0
intnew = 0
for m=n to len(int)-1
if int[m] = int[m+1] - 1
intnew = m+1
flag = 1
nr = nr + 1
else
exit
ok
next
if flag = 1 and nr > 1
if intnew != 0
add(sumint, [n,intnew])
n = m
ok
else
add(sumint, [n,""])
ok
next
showarray(sumint)
 
func showarray(vect)
see "["
svect = ""
for n = 1 to len(vect)
if vect[n][2] != ""
svect = svect +"" + int[vect[n][1]] + "-" + int[vect[n][2]] + ", "
else
svect = svect +"" + int[vect[n][1]] + ", "
ok
next
svect = left(svect, len(svect) - 2)
see svect
see "]" + nl
 

Output:

[-6, -3-1, 3-5, 7-11, 14, 15, 17-20]

Ruby[edit]

def range_extract(l)
# pad the list with a big value, so that the last loop iteration will
# append something to the range
sorted, range = l.sort.concat([Float::MAX]), []
canidate_number = sorted.first
 
# enumerate over the sorted list in pairs of current number and next by index
sorted.each_cons(2) do |current_number, next_number|
# if there is a gap between the current element and its next by index
if current_number.succ < next_number
# if current element is our first or our next by index
if canidate_number == current_number
# put the first element or next by index into our range as a string
range << canidate_number.to_s
else
# if current element is not the same as the first or next
# add [first or next, first or next equals current add , else -, current]
seperator = canidate_number.succ == current_number ? "," : "-"
range << "%d%s%d" % [canidate_number, seperator, current_number]
end
# make the first element the next element
canidate_number = next_number
end
end
range.join(',')
end
 
lst = [
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
]
 
p rng = range_extract(lst)
Output:
"0-2,4,6-8,11,12,14-25,27-33,35-39"


Works with: Ruby version 2.2

Enumerable#slice_when method became usable.

ary = [0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39]
puts ary.sort.slice_when{|i,j| i+1 != j}.map{|a| a.size<3 ? a : "#{a[0]}-#{a[-1]}"}.join(",")
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Rust[edit]

This example does not show the output mentioned in the task description on this page (or a page linked to from here). Please ensure that it meets all task requirements and remove this message.
Note that phrases in task descriptions such as "print and display" and "print and show" for example, indicate that (reasonable length) output be a part of a language's solution.


Iterators are very Rustic. This solution is generic for all numeric types.

use std::ops::Add;
 
struct RangeFinder<'a, T: 'a> {
index: usize,
length: usize,
arr: &'a [T],
}
 
impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<u8, Output=T> + Copy {
type Item = (T, Option<T>);
fn next(&mut self) -> Option<Self::Item> {
if self.index == self.length {
return None;
}
let lo = self.index;
while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + 1 {
self.index += 1
}
let hi = self.index;
self.index += 1;
if hi - lo > 1 {
Some((self.arr[lo], Some(self.arr[hi])))
} else {
if hi - lo == 1 {
self.index -= 1
}
Some((self.arr[lo], None))
}
}
}
 
impl<'a, T> RangeFinder<'a, T> {
fn new(a: &'a [T]) -> Self {
RangeFinder {
index: 0,
arr: a,
length: a.len(),
}
}
}
 
fn main() {
let n = [0,1,2,3];
 
for (i, (lo, hi)) in RangeFinder::new(&n).enumerate() {
if i > 0 {print!(", ")}
print!("{}", lo);
if hi.is_some() {print!("-{}", hi.unwrap())}
}
println!("");
}

Note: You could make the above solution even a little more generic in Nightly Rust (which is version 1.6 at the time of writing) by making the following additions:

Add this to the top of the file:

#![feature(zero_one)]
use std::num::One;

Changing this line:

 impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<u8, Output=T> + Copy {

to this:

impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<T, Output=T> + Copy + One {

And this line:

 while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + 1 {

to this:

 while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + T::one() {

Scala[edit]

object Range {
def spanRange(ls:List[Int])={
var last=ls.head
ls span {x => val b=x<=last+1; last=x; b}
}
 
def toRangeList(ls:List[Int]):List[List[Int]]=ls match {
case Nil => List()
case _ => spanRange(ls) match {
case (range, Nil) => List(range)
case (range, rest) => range :: toRangeList(rest)
}
}
 
def toRangeString(ls:List[List[Int]])=ls map {r=>
if(r.size<3) r mkString ","
else r.head + "-" + r.last
} mkString ","
 
def main(args: Array[String]): Unit = {
var l=List(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
println(toRangeString(toRangeList(l)))
}
}
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Scheme[edit]

Translation of: Qi
 
(define (make-range start end)
(cond ((= start end)
`("," ,start))
((= end (+ start 1))
`("," ,start "," ,end))
(else
`("," ,start "-" ,end))))
 
(define (range-extract-0 start end a)
(cond ((null? a)
(make-range start end))
((= (+ 1 end) (car a))
(range-extract-0 start (car a) (cdr a)))
(else
(append (make-range start end)
(range-extract-0 (car a) (car a) (cdr a))))))
 
(define (range-extract a)
(apply string-append (map (lambda (x)
(if (number? x)
(number->string x)
x))
(cdr (range-extract-0 (car a) (car a) (cdr a))))))
 
(range-extract '( 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
 
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Seed7[edit]

$ include "seed7_05.s7i";
 
const func string: rangeExtraction (in array integer: numbers) is func
result
var string: rangeStri is "";
local
var integer: index is 1;
var integer: index2 is 1;
begin
while index <= length(numbers) do
while index2 <= pred(length(numbers)) and numbers[succ(index2)] = succ(numbers[index2]) do
incr(index2);
end while;
if succ(index) < index2 then
rangeStri &:= "," <& numbers[index] <& "-" <& numbers[index2];
else
while index <= index2 do
rangeStri &:= "," <& numbers[index];
incr(index);
end while;
end if;
incr(index2);
index := index2;
end while;
rangeStri := rangeStri[2 ..];
end func;
 
const proc: main is func
begin
writeln(rangeExtraction([] (0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)));
end func;
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

SNOBOL4[edit]

Translation of: Perl
Works with: Macro Spitbol
Works with: CSnobol

Handles +/- and negative ranges.

*       # Absolute value               
define('abs(n)') :(abs_end)
abs abs = ~(abs = lt(n,0) -n) n :(return)
abs_end
 
define('rangext(str)d1,d2') :(rangext_end)
rangext num = ('+' | '-' | '') span('0123456789')
rxt1 str ',' span(' ') = ' ' :s(rxt1)
rxt2 str num . d1 ' ' num . d2 =
+ d1 ('~,' ? *eq(abs(d2 - d1),1) '~' | ',') d2 :s(rxt2)
rxt3 str ('~' | '-') num '~' = '-' :s(rxt3)
rxt4 str '~' = ',' :s(rxt4)
rangext = str :(return)
rangext_end
 
* # Test and display
test = '0, 1, 2, 4, 6, 7, 8, 11, 12, 14, '
+ '15, 16, 17, 18, 19, 20, 21, 22, 23, 24, '
+ '25, 27, 28, 29, 30, 31, 32, 33, 35, 36, '
+ '37, 38, 39'
output = rangext(test)
end
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Swift[edit]

Works with: Swift version 3
 
import Darwin
 
func ranges(from ints:[Int]) -> [(Int, Int)] {
 
var range : (Int, Int)?
var ranges = [(Int, Int)]()
for this in ints {
if let (start, end) = range {
if this == end + 1 {
range = (start, this)
}
else {
ranges.append(range!)
range = (this, this)
}
}
else { range = (this, this) }
}
ranges.append(range!)
 
return ranges
}
 
func description(from ranges:[(Int, Int)]) -> String {
var desc = ""
for (start, end) in ranges {
desc += desc.isEmpty ? "" : ","
if start == end {
desc += "\(start)"
}
else if end == start + 1 {
desc += "\(start),\(end)"
}
else {
desc += "\(start)-\(end)"
}
}
return desc
}
 
 
let ex = [-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20]
let longer = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]
 
print(description(from: ranges(from: ex)))
print(description(from: ranges(from: longer)))
 
Output:
-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39

Tcl[edit]

proc rangeExtract list {
set result [lindex $list 0]
set first [set last [lindex $list 0]]
foreach term [lrange $list 1 end] {
if {$term == $last+1} {
set last $term
continue
}
if {$last > $first} {
append result [expr {$last == $first+1 ? "," : "-"}] $last
}
append result "," $term
set first [set last $term]
}
if {$last == $first+1} {
append result "," $last
} elseif {$last > $first} {
append result "-" $last
}
return $result
}
 
# Commas already removed so it is a natural Tcl list
puts [rangeExtract {
0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39
}]
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

TXR[edit]

(defun range-extract (numbers)
`@{(mapcar [iff [callf > length (ret 2)]
(ret `@[@1 0][email protected][@1 -1]`)
(ret `@{@1 ","}`)]
(mapcar (op mapcar car)
(split [window-map 1 :reflect
(op list @2 (- @2 @1))
(sort (uniq numbers))]
(op where [chain second (op < 1)])))) ","}`)
Run:
$ txr
This is the TXR Lisp interactive listener of TXR 126.
Use the :quit command or type Ctrl-D on empty line to exit.
1> (load "range.tl")
nil
2> (range-extract '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39))
"0-2,4,6-8,11,12,14-25,27-33,35-39"

TUSCRIPT[edit]

 
$$ MODE TUSCRIPT,{}
MODE DATA
$$ numbers=*
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
$$ MODE TUSCRIPT
numbers=EXCHANGE (numbers,":,{0-00} :':")
unrangednrs=JOIN (numbers,"")
rangednrs=COMBINE (unrangednrs,"")
rangednrs=EXCHANGE (rangednrs,":':,:")
PRINT rangednrs
 

Output:

0-2,4,6-8,11,12,14-25,27-33,35-39

Solution without COMBINE

 
$$ MODE TUSCRIPT
MODE DATA
$$ numbers=*
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
$$ MODE TUSCRIPT
numbers=EXCHANGE (numbers,":,><<> :':")
unrangednrs=JOIN (numbers,"")
 
help = APPEND (unrangednrs, "999999999")
rest = REMOVE (help, 1, n_1)
n_2 = n_1, n_3= n_2 + 1,rangednrs= ""
LOOP n= rest
IF (n!=n_3) THEN
rangednrs = APPEND (rangednrs, n_1)
IF (n_1!=n_2) THEN
range=n_1+1
IF (range==n_2) THEN
rangednrs = APPEND (rangednrs,n_2)
ELSE
rangednrs = CONCAT (rangednrs, "-", n_2)
ENDIF
ENDIF
n_1 = n
ENDIF
n_2 = n, n_3 = n_2 + 1
ENDLOOP
rangednrs=EXCHANGE (rangednrs,":':,:")
PRINT rangednrs
 
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

UNIX Shell[edit]

Works with: bash
#!/usr/bin/bash
 
range_contract () (
add_range () {
case $(( current - range_start )) in
0) ranges+=( $range_start ) ;;
1) ranges+=( $range_start $current ) ;;
*) ranges+=("$range_start-$current") ;;
esac
}
 
ranges=()
range_start=$1
current=$1
shift
 
for number; do
if (( number > current+1 )); then
add_range
range_start=$number
fi
current=$number
done
add_range
 
x="${ranges[@]}"
echo ${x// /,}
)
 
range_contract 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

Ursala[edit]

#import std
#import int
 
x = <0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39>
 
f = mat`,+ ==?(~&l,^|T/~& :/`-)*bhPS+ %zP~~hzX*titZBPiNCSiNCQSL+ rlc ^|E/~& predecessor
 
#show+
 
t = <f x>
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

VBA[edit]

 
Public Function RangeExtraction(AList) As String
'AList is a variant that is an array, assumed filled with numbers in ascending order
Const RangeDelim = "-" 'range delimiter
Dim result As String
Dim InRange As Boolean
Dim Posn, ub, lb, rangestart, rangelen As Integer
 
result = ""
'find dimensions of AList
ub = UBound(AList)
lb = LBound(AList)
Posn = lb
While Posn < ub
rangestart = Posn
rangelen = 0
InRange = True
'try to extend the range
While InRange
rangelen = rangelen + 1
If Posn = ub Then
InRange = False
Else
InRange = (AList(Posn + 1) = AList(Posn) + 1)
Posn = Posn + 1
End If
Wend
If rangelen > 2 Then 'output the range if it has more than 2 elements
result = result & "," & Format$(AList(rangestart)) & RangeDelim & Format$(AList(rangestart + rangelen - 1))
Else 'output the separate elements
For i = rangestart To rangestart + rangelen - 1
result = result & "," & Format$(AList(i))
Next
End If
Posn = rangestart + rangelen
Wend
RangeExtraction = Mid$(result, 2) 'get rid of first comma!
End Function
 
 
Public Sub RangeTest()
'test function RangeExtraction
'first test with a Variant array
Dim MyList As Variant
MyList = Array(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
Debug.Print "a) "; RangeExtraction(MyList)
 
'next test with an array of integers
Dim MyOtherList(1 To 20) As Integer
MyOtherList(1) = -6
MyOtherList(2) = -3
MyOtherList(3) = -2
MyOtherList(4) = -1
MyOtherList(5) = 0
MyOtherList(6) = 1
MyOtherList(7) = 3
MyOtherList(8) = 4
MyOtherList(9) = 5
MyOtherList(10) = 7
MyOtherList(11) = 8
MyOtherList(12) = 9
MyOtherList(13) = 10
MyOtherList(14) = 11
MyOtherList(15) = 14
MyOtherList(16) = 15
MyOtherList(17) = 17
MyOtherList(18) = 18
MyOtherList(19) = 19
MyOtherList(20) = 20
Debug.Print "b) "; RangeExtraction(MyOtherList)
End Sub
 
Output:
RangeTest
a) 0-2,4,6-8,11,12,14-25,27-33,35-39
b) -6,-3-1,3-5,7-11,14,15,17-20

VBScript[edit]

Function Range_Extraction(list)
num = Split(list,",")
For i = 0 To UBound(num)
startnum = CInt(num(i))
sum = startnum
Do While i <= UBound(num)
If sum = CInt(num(i)) Then
If i = UBound(num) Then
If startnum <> CInt(num(i)) Then
If startnum + 1 = CInt(num(i)) Then
Range_Extraction = Range_Extraction & startnum & "," & num(i) & ","
Else
Range_Extraction = Range_Extraction & startnum & "-" & num(i) & ","
End If
Else
Range_Extraction = Range_Extraction & startnum & ","
End If
Exit Do
Else
i = i + 1
sum = sum + 1
End If
Else
If startnum = CInt(num(i-1)) Then
Range_Extraction = Range_Extraction & startnum & ","
Else
If startnum + 1 = CInt(num(i-1)) Then
Range_Extraction = Range_Extraction & startnum & "," & num(i-1) & ","
Else
Range_Extraction = Range_Extraction & startnum & "-" & num(i-1) & ","
End If
End If
i = i - 1
Exit Do
End If
Loop
Next
Range_Extraction = Left(Range_Extraction,Len(Range_Extraction)-1)
End Function
 
WScript.StdOut.Write Range_Extraction("0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39")
Output:
0-2,4,6-8,11,12,14-25,27-33,35-39

zkl[edit]

fcn range(ns){
fcn(w){
if (w.atEnd) return(Void.Stop);
a:=b:=w.next(); n:=0;
while(b+1 == (c:=w.peekN(n))){ n+=1; b=c }
if(n>1){do(n){w.next()}; return("%d-%d".fmt(a,b)); }
a
} :
(0).pump(*,List,_.fp(ns.walker().tweak(Void,Void))).concat(",");
}

The trick here is to use a modified iterator, one that can look past the end of the sequence without puking. The function gathers three or more successive ints (saved as a "a-b" string list element) or just returns the first one (as a number) if it can't. The resulting list is converted to strings separated by commas.

var ns=T(-6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20);
range(ns).println();
 
ns=T(
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
range(ns).println();
 
range([1..100]).println();
Output:
-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39
1-100