Find common directory path: Difference between revisions
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=={{header|AutoHotkey}}== |
=={{header|AutoHotkey}}== |
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<lang autohotkey> |
<lang autohotkey>Dir1 := "/home/user1/tmp/coverage/test" |
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Dir2 := "/home/user1/tmp/covert/operator" |
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Dir3 := "/home/user1/tmp/coven/members" |
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StringSplit, Dir1_, Dir1, / |
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StringSplit, Dir2_, Dir2, / |
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StringSplit, Dir3_, Dir3, / |
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Loop |
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If (Dir1_%A_Index% = Dir2_%A_Index%) |
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And (Dir1_%A_Index% = Dir3_%A_Index%) |
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Result .= (A_Index=1 ? "" : "/") Dir1_%A_Index% |
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Else Break |
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MsgBox, % Result</lang> |
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Message box shows: |
Message box shows: |
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<pre></pre> |
<pre>/home/user1/tmp</pre> |
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=={{header|Clojure}}== |
=={{header|Clojure}}== |
Revision as of 19:34, 19 May 2010
You are encouraged to solve this task according to the task description, using any language you may know.
Create a routine that, given a set of strings representing directory paths and a single character directory separator, will return a string representing that part of the directory tree that is common to all the directories.
Test your routine using the forward slash '/' character as the directory separator and the following three strings as input paths:
'/home/user1/tmp/coverage/test' '/home/user1/tmp/covert/operator' '/home/user1/tmp/coven/members'
Note: The resultant path should be the valid directory '/home/user1/tmp'
and not the longest common string '/home/user1/tmp/cove'
.
If your language has a routine that performs this function (even if it does not have a changeable separator character, then mention it as part of the task)
AutoHotkey
<lang autohotkey>Dir1 := "/home/user1/tmp/coverage/test" Dir2 := "/home/user1/tmp/covert/operator" Dir3 := "/home/user1/tmp/coven/members"
StringSplit, Dir1_, Dir1, / StringSplit, Dir2_, Dir2, / StringSplit, Dir3_, Dir3, /
Loop
If (Dir1_%A_Index% = Dir2_%A_Index%) And (Dir1_%A_Index% = Dir3_%A_Index%) Result .= (A_Index=1 ? "" : "/") Dir1_%A_Index% Else Break
MsgBox, % Result</lang> Message box shows:
/home/user1/tmp
Clojure
<lang clojure>(defn common-prefix [sep paths]
(let [parts-per-path (map #(.split (re-pattern sep) %) paths) common-parts (for [part-list (apply map vector parts-per-path) :when (apply = part-list)] (first part-list))] (apply str (interpose sep common-parts))))
(println
(common-prefix "/" ["/home/user1/tmp/coverage/test" "/home/user1/tmp/covert/operator" "/home/user1/tmp/coven/members"]))</lang>
Factor
<lang factor>: take-shorter ( seq1 seq2 -- shorter )
[ shorter? ] 2keep ? ;
- common-head ( seq1 seq2 -- head )
2dup mismatch [ nip head ] [ take-shorter ] if* ;
- common-prefix-1 ( file1 file2 separator -- prefix )
[ common-head ] dip '[ _ = not ] trim-tail ;
- common-prefix ( seq separator -- prefix )
[ ] swap '[ _ common-prefix-1 ] map-reduce ;</lang>
( scratchpad ) { "/home/user1/tmp/coverage/test" "/home/user1/tmp/covert/operator" "/home/user1/tmp/coven/members" } CHAR: / common-prefix . "/home/user1/tmp/"
J
Solution: <lang j>parseDirs =: = <;.2 ] getCommonPrefix =: ([: *./\ *./@({. ="1 }.)) ;@# {.
getCommonDirPath=: [: getCommonPrefix parseDirs&></lang>
Example: <lang j> paths=: '/home/user1/tmp/coverage/test';'/home/user1/tmp/covert/operator';'/home/user1/tmp/coven/members'
getCommonPrefix >paths
/home/user1/tmp/cove
'/' getCommonDirPath paths
/home/user1/tmp/</lang>
Note: This alternative formulation of parseDirs provides cross-platform support, without the need to specify the path separator. <lang j>parseDirs =: (PATHSEP_j_&= <;.2 ])@jhostpath</lang>
OCaml
<lang ocaml>let rec aux acc paths =
if List.mem [] paths then (List.rev acc) else let heads = List.map List.hd paths in let item = List.hd heads in let all_the_same = List.for_all ((=) item) (List.tl heads) in if all_the_same then aux (item::acc) (List.map List.tl paths) else (List.rev acc)
let common_prefix sep = function
| [] -> invalid_arg "common_prefix" | dirs -> let paths = List.map (Str.split (Str.regexp_string sep)) dirs in let res = aux [] paths in (sep ^ (String.concat sep res))
let () =
let dirs = [ "/home/user1/tmp/coverage/test"; "/home/user1/tmp/covert/operator"; "/home/user1/tmp/coven/members"; ] in print_endline (common_prefix "/" dirs);
- </lang>
(uses the module Str
, str.cma)
Oz
With a few helper functions, we can express the solution like this in Oz: <lang oz>declare
fun {CommonPrefix Sep Paths} fun {GetParts P} {String.tokens P Sep} end Parts = {ZipN {Map Paths GetParts}} EqualParts = {List.takeWhile Parts fun {$ X|Xr} {All Xr {Equals X}} end} in {Join Sep {Map EqualParts Head}} end
fun {ZipN Xs} if {Some Xs {Equals nil}} then nil else {Map Xs Head} | {ZipN {Map Xs Tail}} end end
fun {Join Sep Xs} {FoldR Xs fun {$ X Z} {Append X Sep|Z} end nil} end
fun {Equals C} fun {$ X} X == C end end
fun {Head X|_} X end
fun {Tail _|Xr} Xr end
in
{System.showInfo {CommonPrefix &/ ["/home/user1/tmp/coverage/test" "/home/user1/tmp/covert/operator" "/home/user1/tmp/coven/members"]}}</lang>
PicoLisp
<lang PicoLisp>(de commonPath (Lst Chr)
(glue Chr (make (apply find (mapcar '((L) (split (chop L) Chr)) Lst) '(@ (or (pass <>) (nil (link (next))))) ) ) ) )</lang>
Output:
(commonPath (quote "/home/user1/tmp/coverage/test" "/home/user1/tmp/covert/operator" "/home/user1/tmp/coven/members" ) "/" ) -> "/home/user1/tmp"
PureBasic
PureBasic don't have a path comparator directly but instead have powerful string tools.
Simply by checking the catalog names until they mismatch and add up the correct parts, the task is accomplished. <lang PureBasic>Procedure.s CommonPath(Array InPaths.s(1),separator.s="/")
Protected SOut$="" Protected i, j, toggle If ArraySize(InPaths())=0 ProcedureReturn InPaths(0) ; Special case, only one path EndIf Repeat i+1 toggle=#False For j=1 To ArraySize(InPaths()) If (StringField(InPaths(j-1),i,separator)=StringField(InPaths(j),i,separator)) If Not toggle SOut$+StringField(InPaths(j-1),i,separator)+separator toggle=#True EndIf Else ProcedureReturn SOut$ EndIf Next ForEver
EndProcedure</lang>
Example of implementation <lang PureBasic>Dim t.s(2) t(0)="/home/user1/tmp/coverage/test" t(1)="/home/user1/tmp/covert/operator" t(2)="/home/user1/tmp/coven/members"
Debug CommonPath(t(),"/"))</lang>
Python
The Python os.path.commonprefix function is broken as it returns common characters that may not form a valid directory path: <lang python>>>> import os >>> os.path.commonprefix(['/home/user1/tmp/coverage/test', '/home/user1/tmp/covert/operator', '/home/user1/tmp/coven/members']) '/home/user1/tmp/cove'</lang>
This result can be fixed: <lang python>>>> def commonprefix(*args, sep='/'): return os.path.commonprefix(*args).rpartition(sep)[0]
>>> commonprefix(['/home/user1/tmp/coverage/test', '/home/user1/tmp/covert/operator', '/home/user1/tmp/coven/members']) '/home/user1/tmp'</lang>
But it may be better to not rely on the faulty implementation at all: <lang python>>>> from itertools import takewhile >>> def allnamesequal(name): return all(n==name[0] for n in name[1:])
>>> def commonprefix(paths, sep='/'): bydirectorylevels = zip(*[p.split(sep) for p in paths]) return sep.join(x[0] for x in takewhile(allnamesequal, bydirectorylevels))
>>> commonprefix(['/home/user1/tmp/coverage/test', '/home/user1/tmp/covert/operator', '/home/user1/tmp/coven/members']) '/home/user1/tmp'</lang>
Ruby
Uses the standard library abbrev
module: Given a set of strings, calculate the set of unambiguous abbreviations for those strings, and return a hash where the keys are all the possible abbreviations and the values are the full strings.
<lang ruby>require 'abbrev'
dirs = %w( /home/user1/tmp/coverage/test /home/user1/tmp/covert/operator /home/user1/tmp/coven/members )
common_prefix = dirs.abbrev.keys.min_by {|key| key.length}.chop # => "/home/user1/tmp/cove" common_directory = common_prefix.sub(%r{/[^/]*$}, ) # => "/home/user1/tmp"</lang>
Implementing without that module: <lang ruby>separator = '/' paths = dirs.collect {|dir| dir.split(separator)} uncommon_idx = paths.transpose.each_with_index.find {|dirnames, idx| dirnames.uniq.length > 1}.last common_directory = paths[0][0 ... uncommon_idx].join(separator) # => "/home/user1/tmp"</lang>
Tcl
<lang tcl>package require Tcl 8.5 proc pop {varname} {
upvar 1 $varname var set var [lassign $var head] return $head
}
proc common_prefix {dirs {separator "/"}} {
set parts [split [pop dirs] $separator] while {[llength $dirs]} { set r {} foreach cmp $parts elt [split [pop dirs] $separator] { if {$cmp ne $elt} break lappend r $cmp } set parts $r } return [join $parts $separator]
}</lang>
% common_prefix {/home/user1/tmp/coverage/test /home/user1/tmp/covert/operator /home/user1/tmp/coven/members} /home/user1/tmp
Ursala
The algorithm is to lex the paths into component directory names, and then find the greatest common prefix of those. <lang Ursala>#import std
comdir"s" "p" = mat"s" reduce(gcp,0) (map sep "s") "p"</lang>
where "s"
is a dummy variable representing the separator, "p"
is a dummy variable representing the list of paths, and
sep
is second order function in the standard library that takes a separator character and returns a lexer mapping a string containing the separator to a list of the substrings found between occurrences of itmap
is the conventional mapping combinator, which takes a function operating on items of a list to a function operating pointwise on a whole listgcp
is a polymorphic greatest-common-prefix library function working on pairs of strings or lists of any typereduce
is the standard functional programming reduction combinator, which cumulatively applies a binary operator to a list of operands given the operator and the vacuous case resultmat
is a second order function in the standard library that takes a separator character and returns a function that flattens a list of strings into a single string with copies of the separator inserted between them
Here is a version using operators instead of mnemonics for map
and reduce
.
<lang Ursala>comdir"s" "p" = mat"s" gcp:-0 sep"s"* "p"</lang>
Here is one in partly point-free form, using the composition operator (+
).
<lang Ursala>comdir"s" = mat"s"+ gcp:-0+ sep"s"*</lang>
Here it is in point-free form.
<lang Ursala>comdir = +^/mat gcp:-0++ *+ sep</lang>
test program:
<lang Ursala>#cast %s
test =
comdir`/ <
'/home/user1/tmp/coverage/test', '/home/user1/tmp/covert/operator', '/home/user1/tmp/coven/members'></lang>
output:
'/home/user1/tmp'