Loops/Increment loop index within loop body: Difference between revisions
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Same as Kotlin entry |
Same as Kotlin entry |
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</pre> |
</pre> |
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=={{header|julia}}== |
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Julia's <code>for</code> loop iterator is an Iterator type which cannot be incremented as a simple variable would to change looping. |
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<lang julia>using Primes, Formatting |
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function extraindexincrement(n=42) |
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shown = 0 |
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i = BigInt(n) |
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while shown < n |
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if isprime(i + 1) |
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println("The index is ", format(i, commas=true), " and ", |
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format(i + 1, commas=true), " is prime.") |
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i += i |
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shown += 1 |
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end |
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i += 1 |
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end |
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end |
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extraindexincrement() |
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</lang> {{output}} <pre> |
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The index is 42 and 43 is prime. |
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The index is 88 and 89 is prime. |
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The index is 178 and 179 is prime. |
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The index is 358 and 359 is prime. |
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The index is 718 and 719 is prime. |
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The index is 1,438 and 1,439 is prime. |
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The index is 2,878 and 2,879 is prime. |
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The index is 5,778 and 5,779 is prime. |
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The index is 11,578 and 11,579 is prime. |
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The index is 23,158 and 23,159 is prime. |
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The index is 46,326 and 46,327 is prime. |
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The index is 92,656 and 92,657 is prime. |
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The index is 185,322 and 185,323 is prime. |
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The index is 370,660 and 370,661 is prime. |
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The index is 741,336 and 741,337 is prime. |
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The index is 1,482,706 and 1,482,707 is prime. |
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The index is 2,965,420 and 2,965,421 is prime. |
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The index is 5,930,886 and 5,930,887 is prime. |
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The index is 11,861,790 and 11,861,791 is prime. |
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The index is 23,723,596 and 23,723,597 is prime. |
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The index is 47,447,200 and 47,447,201 is prime. |
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The index is 94,894,426 and 94,894,427 is prime. |
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The index is 189,788,856 and 189,788,857 is prime. |
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The index is 379,577,740 and 379,577,741 is prime. |
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The index is 759,155,482 and 759,155,483 is prime. |
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The index is 1,518,310,966 and 1,518,310,967 is prime. |
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The index is 3,036,621,940 and 3,036,621,941 is prime. |
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The index is 6,073,243,888 and 6,073,243,889 is prime. |
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The index is 12,146,487,778 and 12,146,487,779 is prime. |
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The index is 24,292,975,648 and 24,292,975,649 is prime. |
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The index is 48,585,951,310 and 48,585,951,311 is prime. |
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The index is 97,171,902,628 and 97,171,902,629 is prime. |
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The index is 194,343,805,266 and 194,343,805,267 is prime. |
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The index is 388,687,610,538 and 388,687,610,539 is prime. |
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The index is 777,375,221,080 and 777,375,221,081 is prime. |
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The index is 1,554,750,442,182 and 1,554,750,442,183 is prime. |
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The index is 3,109,500,884,388 and 3,109,500,884,389 is prime. |
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The index is 6,219,001,768,780 and 6,219,001,768,781 is prime. |
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The index is 12,438,003,537,570 and 12,438,003,537,571 is prime. |
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The index is 24,876,007,075,180 and 24,876,007,075,181 is prime. |
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The index is 49,752,014,150,466 and 49,752,014,150,467 is prime. |
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The index is 99,504,028,301,130 and 99,504,028,301,131 is prime. |
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</pre> |
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=={{header|Kotlin}}== |
=={{header|Kotlin}}== |
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Revision as of 08:40, 30 November 2018
You are encouraged to solve this task according to the task description, using any language you may know.
Sometimes, one may need (or want) a loop which
its iterator (the index
variable) is modified within the
loop body in addition to the normal incrementation by the (do) loop structure index.
- Goal
Demonstrate the best way to accomplish this.
- Task
Write a loop which:
- starts the index (variable) at 42
- (at iteration time) increments the index by unity
- if the index is prime:
- displays the index and the prime (to the terminal)
- increments the index such that the new index is now that prime
- terminates the loop when 42 primes are shown
Extra credit: because of the primes get rather large, use commas
within the displayed primes to ease comprehension.
Show all output here.
- Note
Not all programming languages allow the modification of a loop's index. If that is the case, then use whatever method that is appropriate or idiomatic for that language. Please add a note if the loop's index isn't modifiable.
- Related tasks
- Loop over multiple arrays simultaneously
- Loops/Break
- Loops/Continue
- Loops/Do-while
- Loops/Downward for
- Loops/For
- Loops/For with a specified step
- Loops/Foreach
- Loops/Infinite
- Loops/N plus one half
- Loops/Nested
- Loops/While
- Loops/with multiple ranges
- Loops/Wrong ranges
360 Assembly
Assembler 360 provides 3 instructions to create loops: BCT, BXH and BXLE, the register which contains the loop index can be modified at any time. Nothing exceptional for an assembly, banning to modify the loop index begins with high level languages.
This task is a good example of the use of ED instruction to format a number.
For macro use (IF,DO,...), see Structured Macros.
<lang 360asm>* Loops/Increment loop index within loop body - 16/07/2018
LOOPILWB PROLOG
SR R6,R6 i=0
ZAP N,=P'42' n=42
DO WHILE=(C,R6,LT,IMAX) do while(i<imax)
BAL R14,ISPRIME call isprime(n)
IF C,R0,EQ,=F'1' THEN if n is prime then
LA R6,1(R6) i=i+1
XDECO R6,XDEC edit i
MVC PG+2(2),XDEC+10 output i
MVC ZN,EM load edit mask
ED ZN,N edit n
MVC PG+7(L'ZN),ZN output n
XPRNT PG,L'PG print buffer
ZAP WP,N n
AP WP,N +n
SP WP,=P'1' +1
ZAP N,WP n=n+n-1
ENDIF , endif
ZAP WP,N n
AP WP,=P'1' +1
ZAP N,WP n=n+1
ENDDO , enddo
EPILOG
ISPRIME EQU * isprime(n) -----------------------
CP N,=P'2' if n=2
BE RETURN1 then return(1)
CP N,=P'3' if n=3
BE RETURN1 then return(1)
ZAP WDP,N n
DP WDP,=PL8'2' /2
CP WDP+8(8),=P'0' if mod(n,2)=0
BE RETURN0 then return(0)
ZAP WDP,N n
DP WDP,=PL8'3' /3
CP WDP+8(8),=P'0' if mod(n,3)=0
BE RETURN0 then return(0)
ZAP J,=P'5' j=5
LWHILE ZAP WP,J j
MP WP,J *j
CP WP,N while(j*j<=n)
BH EWHILE ~
ZAP WDP,N n
DP WDP,J /j
CP WDP+8(8),=P'0' if mod(n,j)=0
BE RETURN0 then return(0)
ZAP WP,J j
AP WP,=P'2' +2
ZAP WDP,N n
DP WDP,WP n/(j+2)
CP WDP+8(8),=P'0' if mod(n,j+2)=0
BE RETURN0 then return(0)
ZAP WP,J j
AP WP,=P'6' +6
ZAP J,WP j=j+6
B LWHILE loopwhile
EWHILE B RETURN1 return(1) RETURN0 LA R0,0 rc=0
B RETURNX
RETURN1 LA R0,1 rc=1 RETURNX BR R14 return to caller ----------------- IMAX DC F'42' limit EM DC XL20'402020206B2020206B2020206B2020206B202120' mask N DS PL8 n J DS PL8 j PG DC CL80'i=00 : 000,000,000,000,000' buffer XDEC DS CL12 temp for XDECO WP DS PL8 temp for AP,SP,MP WDP DS PL16 temp for DP CW DS CL16 temp for UNPK ZN DS CL20
REGEQU
END LOOPILWB</lang>
- Output:
i= 1 : 43 i= 2 : 89 i= 3 : 179 i= 4 : 359 i= 5 : 719 i= 6 : 1,439 i= 7 : 2,879 i= 8 : 5,779 i= 9 : 11,579 i=10 : 23,159 i=11 : 46,327 i=12 : 92,657 i=13 : 185,323 i=14 : 370,661 i=15 : 741,337 i=16 : 1,482,707 i=17 : 2,965,421 i=18 : 5,930,887 i=19 : 11,861,791 i=20 : 23,723,597 i=21 : 47,447,201 i=22 : 94,894,427 i=23 : 189,788,857 i=24 : 379,577,741 i=25 : 759,155,483 i=26 : 1,518,310,967 i=27 : 3,036,621,941 i=28 : 6,073,243,889 i=29 : 12,146,487,779 i=30 : 24,292,975,649 i=31 : 48,585,951,311 i=32 : 97,171,902,629 i=33 : 194,343,805,267 i=34 : 388,687,610,539 i=35 : 777,375,221,081 i=36 : 1,554,750,442,183 i=37 : 3,109,500,884,389 i=38 : 6,219,001,768,781 i=39 : 12,438,003,537,571 i=40 : 24,876,007,075,181 i=41 : 49,752,014,150,467 i=42 : 99,504,028,301,131
ALGOL 68
In Algol 68, the FOR loop counter cannot be modified in the loop. This uses a WHILE loop testing at the top but is otherwise largely a translation of the Kotlin entry. <lang algol68>BEGIN
# returns TRUE if n is prime, FALSE otherwise #
PROC is prime = ( LONG INT n )BOOL:
IF n MOD 2 = 0 THEN n = 2
ELIF n MOD 3 = 0 THEN n = 3
ELSE
LONG INT d := 5;
BOOL result := TRUE;
WHILE IF d * d > n THEN FALSE
ELIF n MOD d = 0 THEN result := FALSE
ELIF d +:= 2;
n MOD d = 0 THEN result := FALSE
ELSE d +:= 4; TRUE
FI
DO SKIP OD;
result
FI # is prime # ;
LONG INT i := 42;
LONG INT n := 0;
WHILE n < 42 DO
IF is prime( i ) THEN
n +:= 1;
print( ( "n = "
, whole( n, -2 )
, " "
, whole( i, -19 )
, newline
)
);
i +:= i - 1
FI;
i +:= 1
OD
END</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1439 n = 7 2879 n = 8 5779 n = 9 11579 n = 10 23159 n = 11 46327 n = 12 92657 n = 13 185323 n = 14 370661 n = 15 741337 n = 16 1482707 n = 17 2965421 n = 18 5930887 n = 19 11861791 n = 20 23723597 n = 21 47447201 n = 22 94894427 n = 23 189788857 n = 24 379577741 n = 25 759155483 n = 26 1518310967 n = 27 3036621941 n = 28 6073243889 n = 29 12146487779 n = 30 24292975649 n = 31 48585951311 n = 32 97171902629 n = 33 194343805267 n = 34 388687610539 n = 35 777375221081 n = 36 1554750442183 n = 37 3109500884389 n = 38 6219001768781 n = 39 12438003537571 n = 40 24876007075181 n = 41 49752014150467 n = 42 99504028301131
C
The following uses a 'for' rather than a 'do/while' loop but otherwise is similar to the Kotlin entry.
The 'thousands separator' aspect (using the ' flag in printf and setting the locale appropriately) works fine when compiled with gcc on Ubuntu 14.04 but may not work on some other systems as this is not a standard flag. <lang c>#include <stdio.h>
- include <locale.h>
- define LIMIT 42
int is_prime(long long n) {
if (n % 2 == 0) return n == 2;
if (n % 3 == 0) return n == 3;
long long d = 5;
while (d * d <= n) {
if (n % d == 0) return 0;
d += 2;
if (n % d == 0) return 0;
d += 4;
}
return 1;
}
int main() {
long long i;
int n;
setlocale(LC_NUMERIC, "");
for (i = LIMIT, n = 0; n < LIMIT; i++)
if (is_prime(i)) {
n++;
printf("n = %-2d %'19lld\n", n, i);
i += i - 1;
}
return 0;
}</lang>
- Output:
Same as Kotlin entry
C++
<lang cpp>
- include "stdafx.h"
- include <iostream>
- include <math.h>
using namespace std;
bool isPrime(double number) {
for (double i = number - 1; i >= 2; i--) {
if (fmod(number, i) == 0)
return false;
} return true;
} int main() {
double i = 42;
int n = 0;
while (n < 42)
{
if (isPrime(i))
{
n++;
cout.width(1); cout << left << "n = " << n;
//Only for Text Alignment
if (n < 10)
{ cout.width(40); cout << right << i << endl; } else { cout.width(39); cout << right << i << endl; }
i += i - 1;
} i++;
} return 0;
}</lang>
C#
<lang csharp> using System; using System.Globalization;
namespace PrimeNumberLoopcs {
class Program
{
static bool isPrime(double number)
{
for(double i = number - 1; i > 1; i--)
{
if (number % i == 0)
return false;
}
return true;
}
static void Main(string[] args)
{
NumberFormatInfo nfi = new CultureInfo("en-US", false).NumberFormat;
nfi.NumberDecimalDigits = 0;
double i = 42;
int n = 0;
while (n < 42)
{
if (isPrime(i))
{
n++;
Console.WriteLine("n = {0,-20} {1,20}", n, i.ToString("N", nfi));
i += i - 1;
}
i++;
}
}
}
}</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
Factor
Explicit loop indices are non-idiomatic, but Factor is certainly capable of using them. Factor has a for loop near-equivalent, <range> [ ] each, but since it doesn't mesh well with mutation, a while loop is used.
Using two numbers on the data stack
<lang factor>USING: formatting kernel math math.primes tools.memory.private ; IN: rosetta-code.loops-inc-body
42 0 [ dup 42 < ] [
over prime? [
1 + 2dup swap commas
"n = %-2d %19s\n" printf
[ dup + 1 - ] dip
] when
[ 1 + ] dip
] while 2drop</lang>
Using lexical variables
Factor provides lexical variables for situations where they improve readability. <lang factor>USING: formatting kernel math math.primes tools.memory.private ; IN: rosetta-code.loops-inc-body
[let
42 :> i!
0 :> n!
[ n 42 < ] [
i prime? [
n 1 + n!
n i commas "n = %-2d %19s\n" printf
i i + 1 - i!
] when
i 1 + i!
] while
]</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
Fortran
Fortran does not allow to modify the index inside the loop. <lang fortran>do i=1,10
write(*,*) i i=i+1
end do</lang>
Error - I is currently being used as a DO or implied DO control variable Compilation failed.
Fortran 95
<lang fortran>! Loops Increment loop index within loop body - 17/07/2018
integer*8 n
imax=42
i=0; n=42
Do While(i<imax)
If (isprime(n)==1) Then
i=i+1
Write (*,'(I2,1X,I20)') i,n
n=n+n-1
EndIf
n=n+1
EndDo
End
Function isprime(n)
integer*8 n,i
If (n==2 .OR. n==3) Then
isprime=1
return
ElseIf (Mod(n,2)==0 .OR. Mod(n,3)==0) Then
isprime=0
return
Else
i=5
Do While(i*i<=n)
If (Mod(n,i)==0 .OR. Mod(n,i+2)==0) Then
isprime=0
return
EndIf
i=i+6
EndDo
isprime=1
return
EndIf
EndFunction</lang>
- Output:
1 43 2 89 3 179 4 359 5 719 6 1439 7 2879 8 5779 9 11579 10 23159 11 46327 12 92657 13 185323 14 370661 15 741337 16 1482707 17 2965421 18 5930887 19 11861791 20 23723597 21 47447201 22 94894427 23 189788857 24 379577741 25 759155483 26 1518310967 27 3036621941 28 6073243889 29 12146487779 30 24292975649 31 48585951311 32 97171902629 33 194343805267 34 388687610539 35 777375221081 36 1554750442183 37 3109500884389 38 6219001768781 39 12438003537571 40 24876007075181 41 49752014150467 42 99504028301131
Fortran IV
The limit is set to 25 due to the size of integer in Fortran IV. <lang fortran>C LOOPS INCREMENT LOOP INDEX WITHIN LOOP BODY - 17/07/2018
IMAX=25
I=0
N=42
10 IF(I.GE.IMAX)GOTO 30
IF(ISPRIME(N).NE.1)GOTO 20
I=I+1
WRITE(*,301) I,N
301 FORMAT(I2,1X,I10)
N=N+N-1
20 N=N+1
GOTO 10
30 CONTINUE
END
FUNCTION ISPRIME(M)
IF(M.NE.2 .AND. M.NE.3)GOTO 10
ISPRIME=1
RETURN
10 IF(MOD(M,2).NE.0 .AND. MOD(M,3).NE.0)GOTO 20
ISPRIME=0
RETURN
20 I=5
30 IF(I*I.GT.M)GOTO 50
IF(MOD(M,I).NE.0 .AND. MOD(M,I+2).NE.0)GOTO 40
ISPRIME=0
RETURN
40 I=I+6
GOTO 30
50 ISPRIME=1
RETURN
END</lang>
- Output:
1 43 2 89 3 179 4 359 5 719 6 1439 7 2879 8 5779 9 11579 10 23159 11 46327 12 92657 13 185323 14 370661 15 741337 16 1482707 17 2965421 18 5930887 19 11861791 20 23723597 21 47447201 22 94894427 23 189788857 24 379577741 25 759155483
Go
This uses Go's 'for' loop but is otherwise similar to the Kotlin entry.
The 'thousands separator' aspect is dealt with by a couple of external packages (in the 'import' declarations) which can be installed using 'go get'. <lang go>package main
import(
"golang.org/x/text/language" "golang.org/x/text/message"
)
func isPrime(n uint64) bool {
if n % 2 == 0 {
return n == 2
}
if n % 3 == 0 {
return n == 3
}
d := uint64(5)
for d * d <= n {
if n % d == 0 {
return false
}
d += 2
if n % d == 0 {
return false
}
d += 4
}
return true
}
const limit = 42
func main() {
p := message.NewPrinter(language.English)
for i, n := uint64(limit), 0; n < limit; i++ {
if isPrime(i) {
n++
p.Printf("n = %-2d %19d\n", n, i)
i += i - 1
}
}
}</lang>
- Output:
Same as Kotlin entry
J
Fun with j. The verb tacit_loop implements the computation. <lang j> tacit_loop =: _1&(>:@:{`[`]})@:(, (1&p: # _1 2&p.)@:{:)@:]^:(0 ~: (>: #))^:_ x: </lang> Now derive it from the python solution. The monadic verb loop fairly straightforwardly matches the python solution except that loop returns the vector of computed values rather than displays them. <lang j> isPrime =: 1&p: assert 1 1 0 -: isPrime 2 3 4 NB. test and example
loop =: verb define
i =. x: y n =. i. 0 while. y > # n do. if. isPrime i do. n =. n , i i =. _1 2 p. i end. i =. i + 1 end. n
) </lang> Store the vector of indexes using its tail as the current index, removing the `n' variable. In doing so the last item of `i' is not part of the solution, hence change less than to less or equal, and discard the tail value. Also extract the conversion to extended precision x: . <lang J> loop =: verb define@:x:
i =. y
while. y >: # i do.
if. isPrime {: i do.
i =. (, _1 2 p. {:) i
end.
i =. _1 (>:@:{)`[`]} i
end.
}: i
) </lang>
Replace the "if" statement with a computation. This one works by appending onto the solution vector isPrime copies of the proposed new index. <lang J> loop =: verb define@:x:
i =. y
while. y >: # i do.
i =. (, (isPrime # _1 2&p.)@:{:) i
i =. _1 (>:@:{)`[`]} i
end.
}: i
) </lang> Names are an issue brought forth in the j forums. Names have most meaning to the person who wrote them, so there's a bit of J philosophy that says "show the code". J doesn't enforce "code only", and definitions can encapsulate useful chunks of code. If the names I've chosen don't work in your experience or language you could replace them with `a' and `b'. <lang J> save_if_prime =: , (isPrime # _1 2&p.)@:{: increment_tail =: _1&(>:@:{`[`]})
loop =: verb define@:x:
i =. y while. y >: # i do. i =. save_if_prime i i =. increment_tail i end. }: i
) </lang> Why make two assignments when j can increment at save? <lang J> loop =: verb define@:x:
i =. y while. y >: # i do. i =. increment_tail@:save_if_prime i end. }: i
) </lang> Next replace the while loop with double application of J's generalized power conjunction. <lang J> While =: conjunction def 'u^:(0~:v)^:_'
loop =: verb define@:x:
i =. y }: increment_tail@:save_if_prime While(y >: #) i
) </lang> By inspection the variable `i' doesn't contribute anything useful whatsoever. The verb's argument, y, remains. Finally, implemented as an hook verb trains with 'y' and `i' as left ([) and right (]) arguments the complete definitions for tacit_loop are <lang J> isPrime =: 1&p: save_if_prime =: , (isPrime # _1 2&p.)@:{: increment_tail =: _1&(>:@:{`[`]}) While =: conjunction def 'u^:(0~:v)^:_' tacit_loop =: [: }: (increment_tail@:save_if_prime@:]While(>: #) x:) </lang> Include the index numbers with demonstration: <lang J>
9!:37 ] 0 2048 0 222 NB. output control permit lines of 2^11 columns
(>:@:i. ,: tacit_loop) 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
43 89 179 359 719 1439 2879 5779 11579 23159 46327 92657 185323 370661 741337 1482707 2965421 5930887 11861791 23723597 47447201 94894427 189788857 379577741 759155483 1518310967 3036621941 6073243889 12146487779 24292975649 48585951311 97171902629 194343805267 388687610539 777375221081 1554750442183 3109500884389 6219001768781 12438003537571 24876007075181 49752014150467 99504028301131
NB. fix the definition. Here's the code. tacit_loop f.
[: }: (_1&(>:@:{`[`]})@:(, (1&p: # _1 2&p.)@:{:)@:]^:(0 ~: (>: #))^:_ x:)
</lang>
If the loop must require the output side effect, this save_if_prime definition does the trick. Without the output hook it is probably more efficient than the copying version because it evaluates the hook
(, _1 2&p.@:{:)only when isPrime is true.
<lang J>
extra_credit =: ([: }. ,@(',' ,.~ _3 [\ ])&.|.@:":)&>
show =: [ ([: echo@:deb@:({. , ' ' , {:)@:extra_credit # , {:)
save_if_prime =: (, _1 2&p.@:{:)@:show^:(isPrime@:{:)
empty@:tacit_loop 42
1 43 2 89 3 179 4 359 5 719 6 1,439 7 2,879 8 5,779 9 11,579 10 23,159 11 46,327 12 92,657 13 185,323 14 370,661 15 741,337 16 1,482,707 17 2,965,421 18 5,930,887 19 11,861,791 20 23,723,597 21 47,447,201 22 94,894,427 23 189,788,857 24 379,577,741 25 759,155,483 26 1,518,310,967 27 3,036,621,941 28 6,073,243,889 29 12,146,487,779 30 24,292,975,649 31 48,585,951,311 32 97,171,902,629 33 194,343,805,267 34 388,687,610,539 35 777,375,221,081 36 1,554,750,442,183 37 3,109,500,884,389 38 6,219,001,768,781 39 12,438,003,537,571 40 24,876,007,075,181 41 49,752,014,150,467 42 99,504,028,301,131 </lang>
Java
The following uses a 'for' rather than a 'do/while' loop but otherwise is similar to the Kotlin entry. <lang java>public class LoopIncrementWithinBody {
static final int LIMIT = 42;
static boolean isPrime(long n) {
if (n % 2 == 0) return n == 2;
if (n % 3 == 0) return n == 3;
long d = 5;
while (d * d <= n) {
if (n % d == 0) return false;
d += 2;
if (n % d == 0) return false;
d += 4;
}
return true;
}
public static void main(String[] args) {
long i;
int n;
for (i = LIMIT, n = 0; n < LIMIT; i++)
if (isPrime(i)) {
n++;
System.out.printf("n = %-2d %,19d\n", n, i);
i += i - 1;
}
}
}</lang>
- Output:
Same as Kotlin entry
julia
Julia's for loop iterator is an Iterator type which cannot be incremented as a simple variable would to change looping.
<lang julia>using Primes, Formatting
function extraindexincrement(n=42)
shown = 0
i = BigInt(n)
while shown < n
if isprime(i + 1)
println("The index is ", format(i, commas=true), " and ",
format(i + 1, commas=true), " is prime.")
i += i
shown += 1
end
i += 1
end
end
extraindexincrement()
</lang>
- Output:
The index is 42 and 43 is prime. The index is 88 and 89 is prime. The index is 178 and 179 is prime. The index is 358 and 359 is prime. The index is 718 and 719 is prime. The index is 1,438 and 1,439 is prime. The index is 2,878 and 2,879 is prime. The index is 5,778 and 5,779 is prime. The index is 11,578 and 11,579 is prime. The index is 23,158 and 23,159 is prime. The index is 46,326 and 46,327 is prime. The index is 92,656 and 92,657 is prime. The index is 185,322 and 185,323 is prime. The index is 370,660 and 370,661 is prime. The index is 741,336 and 741,337 is prime. The index is 1,482,706 and 1,482,707 is prime. The index is 2,965,420 and 2,965,421 is prime. The index is 5,930,886 and 5,930,887 is prime. The index is 11,861,790 and 11,861,791 is prime. The index is 23,723,596 and 23,723,597 is prime. The index is 47,447,200 and 47,447,201 is prime. The index is 94,894,426 and 94,894,427 is prime. The index is 189,788,856 and 189,788,857 is prime. The index is 379,577,740 and 379,577,741 is prime. The index is 759,155,482 and 759,155,483 is prime. The index is 1,518,310,966 and 1,518,310,967 is prime. The index is 3,036,621,940 and 3,036,621,941 is prime. The index is 6,073,243,888 and 6,073,243,889 is prime. The index is 12,146,487,778 and 12,146,487,779 is prime. The index is 24,292,975,648 and 24,292,975,649 is prime. The index is 48,585,951,310 and 48,585,951,311 is prime. The index is 97,171,902,628 and 97,171,902,629 is prime. The index is 194,343,805,266 and 194,343,805,267 is prime. The index is 388,687,610,538 and 388,687,610,539 is prime. The index is 777,375,221,080 and 777,375,221,081 is prime. The index is 1,554,750,442,182 and 1,554,750,442,183 is prime. The index is 3,109,500,884,388 and 3,109,500,884,389 is prime. The index is 6,219,001,768,780 and 6,219,001,768,781 is prime. The index is 12,438,003,537,570 and 12,438,003,537,571 is prime. The index is 24,876,007,075,180 and 24,876,007,075,181 is prime. The index is 49,752,014,150,466 and 49,752,014,150,467 is prime. The index is 99,504,028,301,130 and 99,504,028,301,131 is prime.
Kotlin
Unlike many other C-family languages (notably Java), Kotlin's 'for' statement doesn't allow either the iteration variable or the step to be modified within the loop body.
So instead we use a do/while loop here which has no such restrictions. <lang scala>// version 1.2.60
fun isPrime(n: Long): Boolean {
if (n % 2L == 0L) return n == 2L
if (n % 3L == 0L) return n == 3L
var d = 5L
while (d * d <= n) {
if (n % d == 0L) return false
d += 2L
if (n % d == 0L) return false
d += 4L
}
return true
}
fun main(args: Array<String>) {
var i = 42L
var n = 0
do {
if (isPrime(i)) {
n++
System.out.printf("n = %-2d %,19d\n", n, i)
i += i - 1
}
i++
}
while (n < 42)
}</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
Although Kotlin is predominantly an object-oriented/procedural language, it does have some features which enable one to program in a functional style. These features include 'tail recursion' which, of course, is commonly used in place of loops in purely functional languages.
In such cases, the Kotlin compiler optimizes out the recursion, leaving behind a fast and efficient loop based version instead.
The following version uses a tail recursive function rather than a while loop to achieve the same effect:
<lang scala>// version 1.2.60
fun isPrime(n: Long): Boolean {
if (n % 2L == 0L) return n == 2L
if (n % 3L == 0L) return n == 3L
var d = 5L
while (d * d <= n) {
if (n % d == 0L) return false
d += 2L
if (n % d == 0L) return false
d += 4L
}
return true
}
tailrec fun loop(index: Long, numPrimes: Int) {
if (numPrimes == 42) return
var i = index
var n = numPrimes
if (isPrime(i)) {
n++
System.out.printf("n = %-2d %,19d\n", n, i)
loop(2 * i - 1, n)
}
else loop(++i, n)
}
fun main(args: Array<String>) {
loop(42, 0)
}</lang>
- Output:
Same as 'while' loop version.
M2000 Interpreter
<lang M2000 Interpreter> Module CheckIt {
Function IsPrime (x) {
if x<=5 OR frac(x) then {
if x == 2 OR x == 3 OR x == 5 then =true
Break
}
if frac(x/2 ) else exit
if frac(x/3) else exit
x1=sqrt(x): d=5
{if frac(x/d ) else exit
d += 2: if d>x1 then =true : exit
if frac(x/d) else exit
d += 4: if d<= x1 else =true: exit
loop
}
}
\\ For Next loops or For {} loops can't change iterator variable (variable has a copy of real iterator)
\\ In those loops we have to use Continue to skip lines and repeat the loop.
\\ so we have to use Block iterator, using Loop which set a flag current block to repeat itself once.
def long Limit=42, n
def currency i
i=Limit
{
if n<limit Else exit
if isPrime(i) then n++ : Print format$("n={0::2}: {1:-20}", n, str$(i,"#,###")) : i+=i-1
i++
loop
}
} CheckIt </lang>
- Output:
Same as Kotlin entry
Maple
A translation of Kotlin entry <lang Maple>i := 42: count := 0: while(count < 42) do i := i+1: if type(i,prime) then count := count + 1: printf("n=%-2d %19d\n", count,i): i := 2*i -1: end if: end do:</lang>
- Output:
n=1 43 n=2 89 n=3 179 n=4 359 n=5 719 n=6 1439 n=7 2879 n=8 5779 n=9 11579 n=10 23159 n=11 46327 n=12 92657 n=13 185323 n=14 370661 n=15 741337 n=16 1482707 n=17 2965421 n=18 5930887 n=19 11861791 n=20 23723597 n=21 47447201 n=22 94894427 n=23 189788857 n=24 379577741 n=25 759155483 n=26 1518310967 n=27 3036621941 n=28 6073243889 n=29 12146487779 n=30 24292975649 n=31 48585951311 n=32 97171902629 n=33 194343805267 n=34 388687610539 n=35 777375221081 n=36 1554750442183 n=37 3109500884389 n=38 6219001768781 n=39 12438003537571 n=40 24876007075181 n=41 49752014150467 n=42 99504028301131
Microsoft Small Basic
Small Basic allows to modify the index inside the loop. <lang smallbasic>'Loops Increment loop index within loop body - 16/07/2018 imax=42 i=0 n=42 While i<imax
isprime_n()
If ret_isprime_n Then
i=i+1
format_i()
format_n()
TextWindow.WriteLine("i="+ret_format_i+" : "+ret_format_n)
n=n+n-1
EndIf
n=n+1
EndWhile
Sub isprime_n
If n=2 Or n=3 Then
ret_isprime_n="True"
ElseIf Math.Remainder(n,2)=0 Or Math.Remainder(n,3)=0 Then
ret_isprime_n="False"
Else
j=5
While j*j<=n
If Math.Remainder(n,j)=0 Or Math.Remainder(n,j+2)=0 Then
ret_isprime_n="False"
Goto exitsub
EndIf
j=j+6
EndWhile
ret_isprime_n="True"
EndIf
exitsub: EndSub 'isprime_n
Sub format_i
ret_format_i=Text.GetSubText(" ",1,3-Text.GetLength(i))+i
EndSub 'format_i
Sub format_n
nn=""
l=-1
For k=Text.GetLength(n) To 1 Step -1
l=l+1
cc=Text.GetSubText(n,k,1)
If l=3 Then
cv=","
l=0
Else
cv=""
EndIf
nn=Text.Append(cc,Text.Append(cv,nn))
EndFor
space=" "
nn=Text.GetSubText(space,1,Text.GetLength(space)-Text.GetLength(nn))+nn
ret_format_n=nn
EndSub 'format_n</lang>
- Output:
i= 1 : 43 i= 2 : 89 i= 3 : 179 i= 4 : 359 i= 5 : 719 i= 6 : 1,439 i= 7 : 2,879 i= 8 : 5,779 i= 9 : 11,579 i=10 : 23,159 i=11 : 46,327 i=12 : 92,657 i=13 : 185,323 i=14 : 370,661 i=15 : 741,337 i=16 : 1,482,707 i=17 : 2,965,421 i=18 : 5,930,887 i=19 : 11,861,791 i=20 : 23,723,597 i=21 : 47,447,201 i=22 : 94,894,427 i=23 : 189,788,857 i=24 : 379,577,741 i=25 : 759,155,483 i=26 : 1,518,310,967 i=27 : 3,036,621,941 i=28 : 6,073,243,889 i=29 : 12,146,487,779 i=30 : 24,292,975,649 i=31 : 48,585,951,311 i=32 : 97,171,902,629 i=33 : 194,343,805,267 i=34 : 388,687,610,539 i=35 : 777,375,221,081 i=36 : 1,554,750,442,183 i=37 : 3,109,500,884,389 i=38 : 6,219,001,768,781 i=39 : 12,438,003,537,571 i=40 : 24,876,007,075,181 i=41 : 49,752,014,150,467 i=42 : 99,504,028,301,131
NewLISP
<lang newlisp>
- ! /usr/local/bin/newlisp
(define (prime? n)
(and (set 'lst (factor n)) (= (length lst) 1)))
(define (thousands_separator i)
(setq i (string i))
(setq len (length i))
(setq i (reverse (explode i)))
(setq o "")
(setq count3 0)
(dolist (x i)
(setq o (string o x))
(inc count3)
(if (and (= 3 count3) (< (+ $idx 1) len))
(begin
(setq o (string o "_"))
(setq count3 0))))
(reverse o))
- - - - Main begins here
(setq i 42) (setq n 0) (while (< n 42)
(if (prime? i)
(begin
(inc n)
(println (string "n = " n " -> " (thousands_separator i)))
(setq i (+ i i -1))))
(inc i)
)
(exit) </lang>
n = 1 -> 43 n = 2 -> 89 n = 3 -> 179 n = 4 -> 359 n = 5 -> 719 n = 6 -> 1_439 n = 7 -> 2_879 n = 8 -> 5_779 n = 9 -> 11_579 n = 10 -> 23_159 n = 11 -> 46_327 n = 12 -> 92_657 n = 13 -> 185_323 n = 14 -> 370_661 n = 15 -> 741_337 n = 16 -> 1_482_707 n = 17 -> 2_965_421 n = 18 -> 5_930_887 n = 19 -> 11_861_791 n = 20 -> 23_723_597 n = 21 -> 47_447_201 n = 22 -> 94_894_427 n = 23 -> 189_788_857 n = 24 -> 379_577_741 n = 25 -> 759_155_483 n = 26 -> 1_518_310_967 n = 27 -> 3_036_621_941 n = 28 -> 6_073_243_889 n = 29 -> 12_146_487_779 n = 30 -> 24_292_975_649 n = 31 -> 48_585_951_311 n = 32 -> 97_171_902_629 n = 33 -> 194_343_805_267 n = 34 -> 388_687_610_539 n = 35 -> 777_375_221_081 n = 36 -> 1_554_750_442_183 n = 37 -> 3_109_500_884_389 n = 38 -> 6_219_001_768_781 n = 39 -> 12_438_003_537_571 n = 40 -> 24_876_007_075_181 n = 41 -> 49_752_014_150_467 n = 42 -> 99_504_028_301_131
Perl
Messing with the loop iterator value doesn't go well in Perl, so use the while loop alternative. The ntheory module is used to test for primes.
<lang perl>use ntheory qw(is_prime);
$i = 42; while ($n < 42) {
if (is_prime($i)) {
$n++;
printf "%2d %21s\n", $n, commatize($i);
$i += $i - 1;
}
$i++;
}
sub commatize {
(my $s = reverse shift) =~ s/(.{3})/$1,/g;
$s =~ s/,$//;
$s = reverse $s;
}</lang>
- Output:
1 43 2 89 3 179 4 359 5 719 6 1,439 7 2,879 8 5,779 9 11,579 10 23,159 11 46,327 12 92,657 13 185,323 14 370,661 15 741,337 16 1,482,707 17 2,965,421 18 5,930,887 19 11,861,791 20 23,723,597 21 47,447,201 22 94,894,427 23 189,788,857 24 379,577,741 25 759,155,483 26 1,518,310,967 27 3,036,621,941 28 6,073,243,889 29 12,146,487,779 30 24,292,975,649 31 48,585,951,311 32 97,171,902,629 33 194,343,805,267 34 388,687,610,539 35 777,375,221,081 36 1,554,750,442,183 37 3,109,500,884,389 38 6,219,001,768,781 39 12,438,003,537,571 40 24,876,007,075,181 41 49,752,014,150,467 42 99,504,028,301,131
Perl 6
Hmm.
Demonstrate the best way to accomplish this.
The best way is probably to not use an explicit loop. Just calculate the sequence directly.
<lang perl6># the actual sequence logic my @seq = grep *.is-prime, (42, { .is-prime ?? $_+<1 !! $_+1 } … *);
- display code
say (1+$_).fmt("%-4s"), @seq[$_].flip.comb(3).join(',').flip.fmt("%20s") for ^42;</lang>
- Output:
1 43 2 89 3 179 4 359 5 719 6 1,439 7 2,879 8 5,779 9 11,579 10 23,159 11 46,327 12 92,657 13 185,323 14 370,661 15 741,337 16 1,482,707 17 2,965,421 18 5,930,887 19 11,861,791 20 23,723,597 21 47,447,201 22 94,894,427 23 189,788,857 24 379,577,741 25 759,155,483 26 1,518,310,967 27 3,036,621,941 28 6,073,243,889 29 12,146,487,779 30 24,292,975,649 31 48,585,951,311 32 97,171,902,629 33 194,343,805,267 34 388,687,610,539 35 777,375,221,081 36 1,554,750,442,183 37 3,109,500,884,389 38 6,219,001,768,781 39 12,438,003,537,571 40 24,876,007,075,181 41 49,752,014,150,467 42 99,504,028,301,131
Phix
Phix does not allow for loop variables to be modified, so we must use a while loop and manual increment for this sort of thing. There is not, as yet, an is_prime() builtin. We can use prime_factors() returns {}, though it is probably a little bit slower as it builds the full list rather than yielding false asap - but at least we don't have to define an is_prime() function. <lang Phix>atom i=42, n=1 while n<=42 do
if prime_factors(i)={} then
printf(1,"n = %-2d %,19d\n", {n, i})
n += 1
i += i-1
end if
i += 1
end while</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
Python
<lang Python>def isPrime(n):
for x in 2, 3:
if not n % x:
return n == x
d = 5
while d * d <= n:
for x in 2, 4:
if not n % d:
return False
d += x
return True
i = 42 n = 0 while n < 42:
if isPrime(i):
n += 1
print('n = {:2} {:20,}'.format(n, i))
i += i - 1
i += 1</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
REXX
<lang rexx>/*REXX pgm displays primes found: starting Z at 42, if Z is a prime, add Z, else add 1.*/ numeric digits 20; d=digits() /*ensure enough decimal digits for Z. */ parse arg limit . /*obtain optional arguments from the CL*/ if limit== | limit=="," then limit=42 /*Not specified? Then use the default.*/ n=0 /*the count of number of primes found. */
do z=42 until n==limit /* ◄──this DO loop's index is modified.*/
if isPrime(z) then do; n=n + 1 /*Z a prime? Them bump prime counter.*/
say right('n='n, 9) right(commas(z), d)
z=z + z - 1 /*also, bump the DO loop index Z. */
end
end /*z*/ /* [↑] a small tribute to Douglas Adams*/
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ commas: parse arg _; do j=length(_)-3 to 1 by -3; _=insert(',', _, j); end; return _ /*──────────────────────────────────────────────────────────────────────────────────────*/ isPrime: procedure; parse arg #; if wordpos(#, '2 3 5 7')\==0 then return 1
if # // 2==0 | # // 3 ==0 then return 0
do j=5 by 6 until j*j>#; if # // j==0 | # // (J+2)==0 then return 0
end /*j*/ /* ___ */
return 1 /*Exceeded √ # ? Then # is prime. */</lang>
- output:
n=1 43
n=2 89
n=3 179
n=4 359
n=5 719
n=6 1,439
n=7 2,879
n=8 5,779
n=9 11,579
n=10 23,159
n=11 46,327
n=12 92,657
n=13 185,323
n=14 370,661
n=15 741,337
n=16 1,482,707
n=17 2,965,421
n=18 5,930,887
n=19 11,861,791
n=20 23,723,597
n=21 47,447,201
n=22 94,894,427
n=23 189,788,857
n=24 379,577,741
n=25 759,155,483
n=26 1,518,310,967
n=27 3,036,621,941
n=28 6,073,243,889
n=29 12,146,487,779
n=30 24,292,975,649
n=31 48,585,951,311
n=32 97,171,902,629
n=33 194,343,805,267
n=34 388,687,610,539
n=35 777,375,221,081
n=36 1,554,750,442,183
n=37 3,109,500,884,389
n=38 6,219,001,768,781
n=39 12,438,003,537,571
n=40 24,876,007,075,181
n=41 49,752,014,150,467
n=42 99,504,028,301,131
Ring
<lang ring>
- Project : Loops/Increment loop index within loop body
load "stdlib.ring" i = 42 n = 0 while n < 42
if isprime(i)
n = n + 1
see "n = " + n + " " + i + nl
i = i + i - 1
ok
i = i + 1
end </lang> Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131
Scala
Like most other Block structured languages (apparently with the exception of Java), Scala's 'for' statement is for the sake of fallibility aka side effect or mutability, limited and doesn't allow either the iteration variable or the step to be modified within the loop body. Both are for serious reasons immutable.
Demonstrate the best way to accomplish this.
So instead we use tail recursion here which, with the use of immutable variables and no side effects, has no such restrictions, and we are save.
- Output:
Best seen running in your browser either by ScalaFiddle (ES aka JavaScript, non JVM) or Scastie (remote JVM).
<lang Scala>import scala.annotation.tailrec
object LoopIncrementWithinBody extends App {
private val (limit, offset) = (42L, 1)
@tailrec
private def loop(i: Long, n: Int): Unit = {
def isPrime(n: Long) =
n > 1 && ((n & 1) != 0 || n == 2) && (n % 3 != 0 || n == 3) &&
((5 to math.sqrt(n).toInt by 2).par forall (n % _ != 0))
if (n < limit + offset)
if (isPrime(i)) {
printf("n = %-2d %,19d%n".formatLocal(java.util.Locale.GERMANY, n, i))
loop(i + i + 1, n + 1)
} else loop(i + 1, n)
}
loop(limit, offset)
}</lang>
Tcl
Inspired by Java and Kotlin variants.
Tcl allows modifying the loop variable. Everything can be implemented straightforward. <lang tcl>proc isPrime n {
if {[expr $n % 2] == 0} {
return [expr $n == 2]
}
if {[expr $n % 3] == 0} {
return [expr $n == 3]
}
for {set d 5} {[expr $d * $d] <= $n} {incr d 4} {
if {[expr $n % $d] == 0} {return 0}
incr d 2
if {[expr $n % $d] == 0} {return 0}
}
return 1
}
set LIMIT 42
for {set i $LIMIT; set n 0} {$n < $LIMIT} {incr i} {
if [isPrime $i] {
incr n
puts "n=$n, i=$i"
incr i [expr $i -1]
}
}</lang>
- Output:
n=1, i=43 n=2, i=89 n=3, i=179 n=4, i=359 n=5, i=719 n=6, i=1439 n=7, i=2879 n=8, i=5779 n=9, i=11579 n=10, i=23159 n=11, i=46327 n=12, i=92657 n=13, i=185323 n=14, i=370661 n=15, i=741337 n=16, i=1482707 n=17, i=2965421 n=18, i=5930887 n=19, i=11861791 n=20, i=23723597 n=21, i=47447201 n=22, i=94894427 n=23, i=189788857 n=24, i=379577741 n=25, i=759155483 n=26, i=1518310967 n=27, i=3036621941 n=28, i=6073243889 n=29, i=12146487779 n=30, i=24292975649 n=31, i=48585951311 n=32, i=97171902629 n=33, i=194343805267 n=34, i=388687610539 n=35, i=777375221081 n=36, i=1554750442183 n=37, i=3109500884389 n=38, i=6219001768781 n=39, i=12438003537571 n=40, i=24876007075181 n=41, i=49752014150467 n=42, i=99504028301131
VBA
Visual Basic for Application (VBA) allows to modify the index inside the loop.
<lang vb> Sub Main()
'Loops Increment loop index within loop body - 17/07/2018
Dim imax, i As Integer
Dim n As Currency
imax = 42
i = 0: n = 42
Do While i < imax
If IsPrime(n) Then
i = i + 1
Debug.Print ("i=" & RightX(i, 2) & " : " & RightX(Format(n, "#,##0"), 20))
n = n + n - 1
End If
n = n + 1
Loop
End Sub 'Main
Function IsPrime(n As Currency)
Dim i As Currency
If n = 2 Or n = 3 Then
IsPrime = True
ElseIf ModX(n, 2) = 0 Or ModX(n, 3) = 0 Then
IsPrime = False
Else
i = 5
Do While i * i <= n
If ModX(n, i) = 0 Or ModX(n, i + 2) = 0 Then
IsPrime = False
Exit Function
End If
i = i + 6
Loop
IsPrime = True
End If
End Function 'IsPrime
Function ModX(a As Currency, b As Currency) As Currency
ModX = a - Int(a / b) * b
End Function 'ModX
Function RightX(c, n)
RightX = Right(Space(n) & c, n)
End Function 'RightX</lang>
- Output:
i= 1 : 43 i= 2 : 89 i= 3 : 179 i= 4 : 359 i= 5 : 719 i= 6 : 1,439 i= 7 : 2,879 i= 8 : 5,779 i= 9 : 11,579 i=10 : 23,159 i=11 : 46,327 i=12 : 92,657 i=13 : 185,323 i=14 : 370,661 i=15 : 741,337 i=16 : 1,482,707 i=17 : 2,965,421 i=18 : 5,930,887 i=19 : 11,861,791 i=20 : 23,723,597 i=21 : 47,447,201 i=22 : 94,894,427 i=23 : 189,788,857 i=24 : 379,577,741 i=25 : 759,155,483 i=26 : 1,518,310,967 i=27 : 3,036,621,941 i=28 : 6,073,243,889 i=29 : 12,146,487,779 i=30 : 24,292,975,649 i=31 : 48,585,951,311 i=32 : 97,171,902,629 i=33 : 194,343,805,267 i=34 : 388,687,610,539 i=35 : 777,375,221,081 i=36 : 1,554,750,442,183 i=37 : 3,109,500,884,389 i=38 : 6,219,001,768,781 i=39 : 12,438,003,537,571 i=40 : 24,876,007,075,181 i=41 : 49,752,014,150,467 i=42 : 99,504,028,301,131
Visual Basic .NET
Visual Basic .Net allows to modify the index inside the loop.
<lang vbnet>Module LoopsIliwlb
Sub Main()
'Loops Increment loop index within loop body - 17/07/2018
Dim imax, i As Int32
Dim n As Int64
imax = 42
i = 0 : n = 42
While i < imax
If IsPrime(n) Then
i = i + 1
Console.WriteLine("i=" & RightX(i, 2) & " : " & RightX(Format(n, "#,##0"), 20))
n = n + n - 1
End If
n = n + 1
End While
End Sub
Function IsPrime(n As Int64)
Dim i As Int64
If n = 2 Or n = 3 Then
IsPrime = True
ElseIf (n Mod 2) = 0 Or (n Mod 3) = 0 Then
IsPrime = False
Else
i = 5
While i * i <= n
If (n Mod i) = 0 Or (n Mod (i + 2)) = 0 Then
IsPrime = False
Exit Function
End If
i = i + 6
End While
IsPrime = True
End If
End Function 'IsPrime
Function RightX(c, n)
RightX = Right(Space(n) & c, n)
End Function
End Module</lang>
- Output:
i= 1 : 43 i= 2 : 89 i= 3 : 179 i= 4 : 359 i= 5 : 719 i= 6 : 1,439 i= 7 : 2,879 i= 8 : 5,779 i= 9 : 11,579 i=10 : 23,159 i=11 : 46,327 i=12 : 92,657 i=13 : 185,323 i=14 : 370,661 i=15 : 741,337 i=16 : 1,482,707 i=17 : 2,965,421 i=18 : 5,930,887 i=19 : 11,861,791 i=20 : 23,723,597 i=21 : 47,447,201 i=22 : 94,894,427 i=23 : 189,788,857 i=24 : 379,577,741 i=25 : 759,155,483 i=26 : 1,518,310,967 i=27 : 3,036,621,941 i=28 : 6,073,243,889 i=29 : 12,146,487,779 i=30 : 24,292,975,649 i=31 : 48,585,951,311 i=32 : 97,171,902,629 i=33 : 194,343,805,267 i=34 : 388,687,610,539 i=35 : 777,375,221,081 i=36 : 1,554,750,442,183 i=37 : 3,109,500,884,389 i=38 : 6,219,001,768,781 i=39 : 12,438,003,537,571 i=40 : 24,876,007,075,181 i=41 : 49,752,014,150,467 i=42 : 99,504,028,301,131
zkl
Uses libGMP (GNU MP Bignum Library) for easy prime detection rather than write that bit of code and pollute this solution. <lang zkl>var [const] BN=Import("zklBigNum"); // libGMP n,p := 1,BN(42); do{
if(p.probablyPrime()){ println("n = %2d %,20d".fmt(n,p)); p.add(p); n+=1; }
p.add(1);
}while(n<=42);</lang> zkl loop variables are iterators that don't allow direct manipulation of their underlying source. The compiler names these iterators __<index>Walker. However, by using the look ahead stack, we can keep the iterator from advancing through the source. <lang zkl>p:=BN(42); foreach n in ([1..42]){
if(p.probablyPrime()){ println("n = %2d %,20d".fmt(n,p)); p.add(p); }
else{ p.add(1); __nWalker.push(n); } // p not prime, don't advance n
}</lang>
- Output:
n = 1 43 n = 2 89 n = 3 179 n = 4 359 n = 5 719 n = 6 1,439 n = 7 2,879 n = 8 5,779 n = 9 11,579 n = 10 23,159 n = 11 46,327 n = 12 92,657 n = 13 185,323 n = 14 370,661 n = 15 741,337 n = 16 1,482,707 n = 17 2,965,421 n = 18 5,930,887 n = 19 11,861,791 n = 20 23,723,597 n = 21 47,447,201 n = 22 94,894,427 n = 23 189,788,857 n = 24 379,577,741 n = 25 759,155,483 n = 26 1,518,310,967 n = 27 3,036,621,941 n = 28 6,073,243,889 n = 29 12,146,487,779 n = 30 24,292,975,649 n = 31 48,585,951,311 n = 32 97,171,902,629 n = 33 194,343,805,267 n = 34 388,687,610,539 n = 35 777,375,221,081 n = 36 1,554,750,442,183 n = 37 3,109,500,884,389 n = 38 6,219,001,768,781 n = 39 12,438,003,537,571 n = 40 24,876,007,075,181 n = 41 49,752,014,150,467 n = 42 99,504,028,301,131