improved comments in LZW.pm, fixed trivial thing in encdecode..

2 files changed, 13 insertions, 1 deletions

diff --git a/challenge-022/duncan-c-white/perl5/LZW.pm b/challenge-022/duncan-c-white/perl5/LZW.pm
index ced6381511..5dac1ca36e 100644
--- a/challenge-022/duncan-c-white/perl5/LZW.pm
+++ b/challenge-022/duncan-c-white/perl5/LZW.pm
@@ -11,6 +11,17 @@
 # quite clear is what initial alphabet both encoding and decoding should
 # use?  but let's have a go anyway, hopefully building an encoder will
 # start to clarify most things?
+#
+# Update: the encoding was very straight forward, but I struggled for
+# several hours to get my head around the decoding - especially the
+# special case described in the wikipedia page where the dictionary
+# doesn't contain the entry.  The description was NOT CLEAR ENOUGH
+# in that case (and giving an example text where the special case
+# applied would have helped a lot, eg TOTOTOT was the shortest I found)
+#
+# Eventually, with time running out, I checked some Rosetta code
+# implementations, discovered what pseudo-code the description
+# really mapped onto, and adapted it to fit my code..
 # 
 
 use strict;
diff --git a/challenge-022/duncan-c-white/perl5/encdecode.pl b/challenge-022/duncan-c-white/perl5/encdecode.pl
index b8bc99a774..24e7916c4a 100755
--- a/challenge-022/duncan-c-white/perl5/encdecode.pl
+++ b/challenge-022/duncan-c-white/perl5/encdecode.pl
@@ -26,8 +26,9 @@ lzw_setdebug( 0 );
 die "Usage: encdecode STRING\n" unless @ARGV==1;
 my $text = shift;
 
+$text .= '#' unless substr($text,length($text)-1) eq '#';
+
 my $binstr = lzw_encode( $text );
-#$text .= '#';
 print "\ntext: $text\n" if 0;
 #print "  encodes to: $binstr\n";
 my $text2 = lzw_decode( $binstr );