(New diff) Re: [m-rev.] Handle polymorphic inequality goals

[Fergus Henderson]

On 29-Oct-2002, Ralph Becket <rafe at cs.mu.OZ.AU> wrote:
> 
> Make the Prolog term comparison operators (@<, @=<, @>, @>=) 
> builtin since they're often useful and calling compare/3
> can look a little awkward.
>
> Simplification now applies the following transformations on the
> new builtin operators:
> 
> 	X  @< Y    --->    some [R] (compare(R, X, Y), R  = (<))
> 	X @=< Y    --->    some [R] (compare(R, X, Y), R \= (>))
> 	X @>  Y    --->    some [R] (compare(R, X, Y), R  = (>))
> 	X @>= Y    --->    some [R] (compare(R, X, Y), R \= (<))

(Ideally it would have been best to post these two -- the library change
and the optimization -- as two separate patches.)

A test case would be a good idea.

> compiler/goal_util.m:
> 	Added a new parameter, ModeNo, to goal_util__generate_simple_call.
> 	ModeNo is either
> 	- `only_mode' in which case the predicate in question is expected to
> 	  have exactly one mode or
> 	- `mode_no(N)' in which case mode number N (counting from 0) is
> 	  used.
> 	The inequality transformation uses this to handle calls to compare/3
> 	with unique arguments (even though the builtin inequality modes don't
> 	yet handle ui arguments...)

Hmm... 

> Index: NEWS
> ===================================================================
> RCS file: /home/mercury1/repository/mercury/NEWS,v
> retrieving revision 1.274
> diff -u -r1.274 NEWS
> --- NEWS	22 Oct 2002 13:10:33 -0000	1.274
> +++ NEWS	28 Oct 2002 05:07:28 -0000
> @@ -12,6 +12,7 @@
>  * Support for defining predicates or functions
>    using different clauses for different modes.
>  * Support for Haskell-like "@" expressions.
> +* Prolog-style term comparison operators, @<, @=<, @>, @>=, are now builtin.

That should go in the "library" changes section, IMHO.

> Index: compiler/simplify.m
...
> +			    "replacment of inequality with call to compare/3"),
> +			[]),

s/replacment/replacement/

Otherwise that looks fine.


-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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