Re: Pattern-matching destructors ?

Re: Pattern-matching destructors ?

[Jeff Shaw]

If you're matching against a record, you can omit the values you don't 
care about. For instance:

type test = {a : int; b : int}

let testfun = function {a=x; b= y} when x=y -> "same" | {a=x} -> ("a is 
" ^ string_of_int x);;

I'm not sure if this helps you but it's the first thing I thought off.

Pattern-matching destructors ?

[David Teller]

   Hi everyone,

 I'm currently working on static analysis of JavaScript 2. For this, I
need to keep lots of informations in each node of my AST, including
things such as line/column (for better error messages), unique
identifier (for storing inferred information), etc. As things progress,
I fear that the number of such informations is growing prohibitive and
very much getting into the way of pattern-matching.

 However, I do remember reading on this list a discussion regarding the
possibility of extending pattern-matching so as to allow matching
against user-defined criteria rather than constructors -- I'm afraid I
don't remember the name of these criteria, possibly "destructors" or
"queries".

 As far as I remember this discussion, the feature was present in F# (or
at least planned), but not in OCaml. Could anyone tell me if things have
evolved on the OCaml side, perhaps with a little camlp4 magic ? 


Thanks in advance,
 David

-- 
David Teller ------------------------------------------
Security of Distributed Systems -----------------------
-- http://www.univ-orleans.fr/lifo/Members/David.Teller
----- Laboratoire d'Informatique Fondamentale d'Orleans