tidied into 3-liner (init, code, return)

1 files changed, 58 insertions, 13 deletions

diff --git a/challenge-112/james-smith/perl/ch-1.pl b/challenge-112/james-smith/perl/ch-1.pl
index 33bad261ca..c95592a90a 100644
--- a/challenge-112/james-smith/perl/ch-1.pl
+++ b/challenge-112/james-smith/perl/ch-1.pl
@@ -6,22 +6,67 @@ use warnings;
 use feature qw(say);
 use Test::More;
 
-is( can_path('/a/'), '/a' );
-is( can_path('/a/b//c/'), '/a/b/c' );
-is( can_path('/a/./b/./c/'), '/a/b/c' );
-is( can_path('/a/b/c/../..'), '/a' );
-is( can_path('/a/b/../c/..'), '/a' );
-is( can_path('/a/../b/../c/..'), '/' );
-is( can_path('/a/../b/../c/..'), '/' );
-is( can_path('/a/../b/../c/../../..'), '/' );
-is( can_path('/a/../b/../c/../../..'), '/' );
-is( can_path('/../../../a/'), '/a' );
+is( canonical_path('/a/'),                   '/a',     'Remove trailing slash (empty trailing dir)' );
+is( canonical_path('//a'),                   '/a',     'Remove empty dir as start' );
+is( canonical_path('/a/b//c/'),              '/a/b/c', 'Remove empty dir "//"' );
+is( canonical_path('/a/./b/./c/'),           '/a/b/c', 'Remove "." dir ...' );
+is( canonical_path('/a/b/c/../..'),          '/a',     'Two ".." together at end' );
+is( canonical_path('/a/b/../c/..'),          '/a',     'Two ".." separated (one in middle)' );
+is( canonical_path('/a/../b/../c/./.'),      '/c',     'Two ".." separated (both in middle)' );
+is( canonical_path('/a/b/../../c'),          '/c',     'Two ".." together in middle' );
+is( canonical_path('/a/../b/../c/..'),       '/',      'Same no of ".." as dir' );
+is( canonical_path('/a/b/c/../../..'),       '/',      'Same no of ".." as dir - all at end' );
+is( canonical_path('/a/../b/../c/../../..'), '/',      'More ".." than dirs' );
+is( canonical_path('/../../../a/'),          '/a',     '".." at start, no other ".."' );
+is( canonical_path('/../../a/../c/.'),       '/c',     '".." at start, other ".."' );
+
+is( canonical_path_compact('/a/'),                   '/a',     'Remove trailing slash (empty trailing dir)' );
+is( canonical_path_compact('//a'),                   '/a',     'Remove empty dir as start' );
+is( canonical_path_compact('/a/b//c/'),              '/a/b/c', 'Remove empty dir "//"' );
+is( canonical_path_compact('/a/./b/./c/'),           '/a/b/c', 'Remove "." dir ...' );
+is( canonical_path_compact('/a/b/c/../..'),          '/a',     'Two ".." together at end' );
+is( canonical_path_compact('/a/b/../c/..'),          '/a',     'Two ".." separated (one in middle)' );
+is( canonical_path_compact('/a/../b/../c/./.'),      '/c',     'Two ".." separated (both in middle)' );
+is( canonical_path_compact('/a/b/../../c'),          '/c',     'Two ".." together in middle' );
+is( canonical_path_compact('/a/../b/../c/..'),       '/',      'Same no of ".." as dir' );
+is( canonical_path_compact('/a/b/c/../../..'),       '/',      'Same no of ".." as dir - all at end' );
+is( canonical_path_compact('/a/../b/../c/../../..'), '/',      'More ".." than dirs' );
+is( canonical_path_compact('/../../../a/'),          '/a',     '".." at start, no other ".."' );
+is( canonical_path_compact('/../../a/../c/.'),       '/c',     '".." at start, other ".."' );
 
 done_testing();
 
-sub can_path {
-  my($p,@parts) = (1,grep { $_ ne '' && $_ ne '.' } split m{/}, $_[0]);
-  $parts[$p] ne '..' ? $p++ : $p>0 ? splice @parts,--$p,2 : shift @parts while $p < @parts;
+sub canonical_path {
+  ## Initialize:
+  ##   Set pointer to 1;
+  ##   Split path into directories
+  ##     - remove empty directories and also "." directories {current dir}
+
+  my( $p, @parts ) = ( 1, grep { $_ ne '' && $_ ne '.' } split m{/}, $_[0] );
+
+  ## Process paths...
+  ## If the directory isn't ".." we just move on to the next one...
+  ## If it is the first entry of the list we just shift it off.
+  ## Otherwise we splice it out of the array, along withe previous directory
+  ##     `splice @parts, $p-1, 2`
+  ##   and then backtrack one space..
+  ##   this means the splice can be written as:
+  ##     `splice @parts, --$p, 2`
+  ## Repeat this until we get to the end of the array - there will be no more '..'s in the
+  ## list...
+
+  $parts[$p] ne '..' ? $p++ : $p ? splice @parts, --$p, 2 : shift @parts while $p < @parts;
+
+  ## Finally return our string which consists of a "/" followed by all the
+  ## directories left joing with "/"s...
+
   return '/'.join '/',@parts;
 }
 
+sub canonical_path_compact {
+my($p,@d)=(1,grep {''ne$_&&'.'ne$_}split/\//,shift);
+$d[$p]ne'..'?$p++:$p?splice@d,--$p,2:shift@d while$p<@d;
+'/'.join'/',@d;
+}
+
+