[m-rev.] for review: generalize the specialization of compare/3 predicates

[Zoltan Somogyi]

On 05-Feb-2002, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > @@ -1069,52 +1063,32 @@
> >  				Ctor, Res, H1, H2,
> >  				Context, Clauses)
> >  		;
> > -			unify_proc__generate_du_general_compare_clauses(Type,
> > +			unify_proc__generate_du_linear_compare_clauses(Type,
> >  				Ctors, Res, H1, H2, Context, Clauses)
> >
> >  	;
> > -		{ Ctors = [Ctor1, Ctor2] },
> > +		{ Ctors = [_, _ | _] },
> 
> Can't you remove the special case handling of the single
> constructor case as well?

Yes, but that case is already handled by code above this diff.

> >  		{ globals__lookup_int_option(Globals, compare_specialization,
> >  			CompareSpec) },
> > -		( { CompareSpec >= 2 } ->
> > -			unify_proc__generate_du_two_compare_clauses(
> > -				Ctor1, Ctor2, Res, H1, H2,
> > -				Context, Clauses)
> > -		;
> > -			unify_proc__generate_du_general_compare_clauses(Type,
> > +		{ list__length(Ctors, NumCtors) },
> > +		( { CompareSpec >= NumCtors } ->
> > +			unify_proc__generate_du_quad_compare_clauses(
> >  				Ctors, Res, H1, H2, Context, Clauses)
> 
> The comparison would be slightly easier to read with the constant
> (CompareSpec) on the right.

OK, I will flip them around.

> I'd also suggest not abbreviating "quadratic".

The predicates names are already very long.

> > +unify_proc__generate_du_quad_compare_clauses_2(_LeftCtor,
> > +		[], _Cmp, _R, _X, _Y, _Context, Cases, Cases) --> [].
> > +unify_proc__generate_du_quad_compare_clauses_2(LeftCtor,
> > +		[RightCtor | RightCtors], Cmp0, R, X, Y, Context,
> > +		Cases0, Cases) -->
> > +	( { LeftCtor = RightCtor } ->
> > +		unify_proc__generate_compare_case(LeftCtor, R, X, Y, Context,
> > +			Case),
> > +		{ Cmp1 = "<" }
> > +	;
> > +		unify_proc__generate_asymmetric_compare_case(LeftCtor,
> > +			RightCtor, Cmp0, R, X, Y, Context, Case),
> > +		{ Cmp1 = Cmp0 }
> > +	),
> > +	unify_proc__generate_du_quad_compare_clauses_2(LeftCtor, RightCtors,
> > +		Cmp1, R, X, Y, Context, [Case | Cases0], Cases).
> 
> It might be slightly better to reverse the list of cases so
> they are in sorted order.

The order will disappear anyway at switch detection time.

Are you concerned about how the code appears before then?

Zoltan.
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