in reply to (Golf) Cryptographer's Tool #1
Here's my shot at it; 68 chars:
sub c { ($_,$a)=@_; map{$h{$_}?$h{$_}:do{$h{$_}=(split//,$a)[$i++]."\0"}}/./g }
Update:
Here's another at 66. This one takes a completely different approach--it removes all duplicates of letters(the long part), then does a simple translation on them (the easy part). Here it is:
sub c { ($_,$a)=@_;$b=$_; 1 while$b=~s/(.)(.*?)\1/$1$2/g; eval"y/$b/$a/"; $_ }
Update2:Good catch tilly. This makes it too long to contend, but here's the revised version:
sub c { ($_,$a)=@_;$b=$_; 1 while$b=~s/(.)(.*?)\1/$1$2/g; eval"y/\Q$b\E/\Q$a\E/"; $_ }
The 15 year old, freshman programmer,
Stephen Rawls
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Meditations