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Re: [Caml-list] Pattern matcher no more supposed to warn on non
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Date: -- (:)
From: Luc Maranget <luc.maranget@i...>
Subject: Re: [Caml-list] Pattern matcher no more supposed to warn on non
> 
> 
> So long as the issue of when clauses has come up,
Well I am thinking about it, others complain loudly.



> 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,
You bet.
> 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 |

Argl....

Dear Dan, which result would you consider to be correct ?
(1111 ?)
Please tell me...
(Note that I see no consitency either in 3.02 or 3.00,)

Cheers, thanks,  and argl again !

--Luc

It is worth a warning in the manual, at least...

> 
> ===============
> 
> 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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