Re: [Caml-list] Request for complete pattern matching

[skaller <skaller@users.sourceforge.net>]

On Wed, 2005-11-23 at 12:56 -0800, Martin Jambon wrote:

> (* toto.ml *)
> try
>    while true do
>      match read_line () with
>  	/ upper / | / _* "." eos / -> print_endline "looks like a sentence"
>        | "." | / ("bye"~ space*)+ / -> print_endline "Bye!"; exit 0
>        | _ -> print_endline "???"
>    done
> with End_of_file -> ()
> 
> Notes:
> - the stuff between slashes are regexps
> - "." and the last _ are regular OCaml patterns
> - regexps are replaced by an identifier which is matched after the 
> arrow using library functions, then it is decided whether to jump to the 
> next case or to execute the user-given expression.

Why can't this be done with 'when' clause?

EG:

	| ... predicate ... -> ...

replace by 

	| ... variable .. when predicate(variable)

This would seem to fail only in that 'predicate' code
cannot refer to another predicate, since the variable
name is not known.

The 'break' implementation, however, may be overtly
more efficient (save duplicating predicate evaluations).

-- 
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net