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https://github.com/Mercury-Language/mercury.git
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9f7d8305a6
compiler/switch_detection.m:
As above.
tests/valid/preferred_switch_var.m:
A new test case. With the compiler before this change, it did not compile,
because
(a) switch detection transformed the disjunction in the
"require_switch_arms_semidet [T]" scope into a switch on U instead
of T, because the switch on U is cannot_fail while the switch on T
is can_fail, and
(b) having a switch on U inside the "require_switch_arms_semidet [T]" scope
got an error about the goal not being a switch on T.
tests/valid/Mmakefile:
Enable the new test case.
58 lines
1.4 KiB
Mathematica
58 lines
1.4 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%---------------------------------------------------------------------------%
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%
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% The following program tests whether the presence of a require_switch_arms_X
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% scope can get the compiler to recognize the switch inside the scope as
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% being an incomplete switch on the named variable, even though it could
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% also recognize it as a *complete* switch on another variable.
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%
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% Normally, switch detection prefers complete switches to incomplete ones,
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% but a scope that programmers use to specify the variable that they *expect*
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% the switch to be switch on should trump that.
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%
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%---------------------------------------------------------------------------%
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:- module preferred_switch_var.
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:- interface.
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:- type t
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---> t1
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; t2
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; t3
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; t4
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; t5
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; t6
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; t7
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; t8.
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:- type u
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---> u1
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; u2.
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:- pred p(t::in, u::in, int::out) is semidet.
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%---------------------------------------------------------------------------%
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:- implementation.
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p(T, U, N) :-
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require_switch_arms_semidet [T]
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(
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T = t1,
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U = u1,
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N = 11
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;
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T = t2,
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U = u2,
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N = 22
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;
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T = t3,
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U = u1,
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N = 31
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;
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T = t4,
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U = u2,
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N = 42
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).
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