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From: Dan Grossman <danieljg@cs.cornell.edu>
To: caml-list <caml-list@inria.fr>
Subject: Re: [Caml-list] Pattern matcher no more supposed to warn on non  exhaustive patterns ?
Date: Wed, 03 Oct 2001 12:54:59 -0400	[thread overview]
Message-ID: <3BBB42E3.C8477709@cs.cornell.edu> (raw)
In-Reply-To: <007201c14c32$37e4c5a0$060000c0@N7YYB>


So long as the issue of when clauses has come up, I'll also point out that
the pattern-compiler essentially assumes that when clauses are pure.  I'm
not complaining because I consider it poor style to violate this assumption,
but I've never heard it discussed anywhere.

For the program below, ocamlopt version 3.00 produces a program that prints
1314.

--Dan

-- 
| Dan Grossman     www.cs.cornell.edu/home/danieljg H:607 256 0724 |
| 5157 Upson Hall  danieljg@cs.cornell.edu          O:607 255 9834 |

===============

type y = {mutable c:bool}
type x = {a:y; b:y}

let f1 (v:x) = 
  match v with
    {a = _; b = _} when (v.a.c <- false; v.b.c <- false; false) -> 0
  | {a = {c=false}; b = {c=false}} -> 1
  | {a = {c=false}; b = {c=true}}  -> 2
  | {a = {c=true};  b = {c=false}} -> 3
  | {a = {c=true};  b = {c=true}}  -> 4

let f2 (v:x) = 
  match v with
    {a = {c=true}; b = _} when (v.a.c <- false; v.b.c <- false; false) -> 0
  | {a = {c=false}; b = {c=false}} -> 1
  | {a = {c=false}; b = {c=true}}  -> 2
  | {a = {c=true};  b = {c=false}} -> 3
  | {a = {c=true};  b = {c=true}}  -> 4

let f3 (v:x) = 
  match v with
    {a = _; b = {c=true}} when (v.a.c <- false; v.b.c <- false; false) -> 0
  | {a = {c=false}; b = {c=false}} -> 1
  | {a = {c=false}; b = {c=true}}  -> 2
  | {a = {c=true};  b = {c=false}} -> 3
  | {a = {c=true};  b = {c=true}}  -> 4

let f4 (v:x) = 
  match v with
    {a = {c=true}; b={c=true}} when (v.a.c <- false; v.b.c <- false; false)
-> 0
  | {a = {c=false}; b = {c=false}} -> 1
  | {a = {c=false}; b = {c=true}}  -> 2
  | {a = {c=true};  b = {c=false}} -> 3
  | {a = {c=true};  b = {c=true}}  -> 4

let main () =
  let v1:x = {a = {c=true}; b = {c=true}} in
  let v2:x = {a = {c=true}; b = {c=true}} in
  let v3:x = {a = {c=true}; b = {c=true}} in
  let v4:x = {a = {c=true}; b = {c=true}} in
  print_int (f1 v1);
  print_int (f2 v2);
  print_int (f3 v3);
  print_int (f4 v4)

let _ = main ()
-------------------
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  reply	other threads:[~2001-10-03 16:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-10-03 17:37 Jean-Marc Eber
2001-10-03 16:54 ` Dan Grossman [this message]
2001-10-03 18:07   ` [Caml-list] Pattern matcher no more supposed to warn on non Luc Maranget
2001-10-03 18:23     ` Dan Grossman
2001-10-03 20:52   ` [Caml-list] Pattern matcher no more supposed to warn on non exhaustive patterns ? Pierre Weis
2001-10-04  7:55 ` Luc Maranget
2001-10-04  9:06   ` Luc Maranget
2001-10-04  4:29 Gregory Morrisett
2001-10-04  7:06 ` Luc Maranget
2001-10-04  8:17 ` Jacques Garrigue
2001-10-04 12:28 ` Xavier Leroy
2001-10-04  7:36 Damien Doligez
2001-10-04  7:51 ` Einar Karttunen

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