[mercury-users] Disjunctions vs. multiple head clauses

[Peter Hawkins]

Hi...

Is there any difference in efficiency between the two predicates bar1 and bar2 
in the following? In Prolog there would (usually) be, but does the same apply 
to Mercury?

:- type foo ---> fa ; fb ; fc ; fd ; ... ; fz.

:- pred bar1(foo, int).
:- mode bar1(in, out) is det.

bar1(fa, 1).
bar1(fb, 2).
bar1(fc, 3).
...
bar1(fz, 26).

:- pred bar2(foo, int).
:- mode bar2(in, out) is det.

bar2(F, N) :-
	(F = fa, N = 1
	; F = fb, N = 2
	; ...
	; F = fz, N = 26
	).

(obviously the actual code I'm interested in would be more complex than this 
toy example)

Thanks,
Peter
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