In search of a kind of converse to sub/gsub

Axel asked for a method find_what_to_replace

... such that for

replace_what_substring,replace_it_by
=string1.find_what_to_replace(string2)

the statement

string2 == string1.gsub(replace_what_substring,replace_it_by)

holds true .

Has anybody done that already?

Does Diff::LCS do what you want? It returns the differences between strings.
(You can get it from http://rubyforge.org/frs/?group_id=84 or via rubygems)

Cheers,
Dave

Thank you , Dave - that's 100 out of 100 points!

Best regards,

Axel