[Haskell-beginners] editing a list

[Stephen Tetley]

What the original author appears to want is "string rewriting".

Dave Bayer had a nice implementation in this thread...

http://www.haskell.org/pipermail/beginners/2010-February/003399.html

His question was actually about something else, but the continuation
of the thread illuminates his technique, see my reply and the messages
following it up:

http://www.haskell.org/pipermail/beginners/2010-February/003433.html

String rewriting is not particularly straight-forward in Haskell
because you are consuming the input string and generating output at
"different speeds" so using direct recursion and pattern matching
makes for monolithic code. By "different speeds" I mean you might want
to look at one or several characters in the input to match a token,
and produce zero, one or many characters as output at each rewrite
step.