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Date: Wed, 02 Oct 2002 16:12:34 +0200
From: Alessandro Baretta <alex@baretta.com>
Organization: Baretta srl -- www.baretta.com
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To: Ocaml <caml-list@inria.fr>
Subject: [Caml-list] Pattern matching and strings
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I have to do a little bit of pattern matching on strings. My 
first instict was to write something like the following.

let foo x = ...
let bar x = ...
... = function
| "foo" ^ rest -> foo rest
| "bar" ^ rest -> bar rest
| _ -> raise Unrecognized

Of course, this is not possible because (^) is an operator 
rather than a constructor. Since I believe that the above 
code is much more natural and idiomatic than code based on 
regexps, I wonder how much compiler magic it would take to 
make it work. Probably all it takes is some syntax-magic 
since the above can be mapped onto the following:

open Scanf

... = function x -> begin
   try sscanf x "foo%[^]" foo with Scan_failure _ ->
   try sscanf x "bar%[^]" bar with Scan_failure _ ->
     raise Unrecognized
end

An equivalent mapping could be done with the Str library or 
any other regexp library.

However, the former is much cleaner. If it could be had, I'd 
appreciate it.

Alex

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