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https://github.com/Mercury-Language/mercury.git
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4413ebe829
Estimated hours taken: 0.25 tests/hard_coded/bidirectional.m: tests/hard_coded/cycles.m: Add `import_module char', needed for type `char'. (Previously, before Simon's changes to implement `:- use_module', the compiler incorrectly allowed these illegal programs, because types were imported transitively. That bug is not completely fixed, but now such types are only imported as if by `:- use_module' rather than `:- import_module', so the compiler now catches such errors if the type name is not explicitly module-qualified.)
135 lines
3.8 KiB
Mathematica
135 lines
3.8 KiB
Mathematica
% This is a regression test: Mercury 0.6 generated bad code for this
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% example. (The generated code went into an infinite loop resulting
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% in a nondet stack overflow.)
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% cycles.m
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%===========================================================================
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:- module cycles.
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%---------------------------------------------------------------------------
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:- interface.
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:- import_module io.
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:- pred main(io__state::di, io__state::uo) is det.
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%---------------------------------------------------------------------------
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:- implementation.
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:- import_module list, bool, std_util, char.
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%--------------------------------------------------
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:- type node ---> a ; b ; c ; d ; e ; f ; g ; h ; i ; j ; k ; l.
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:- type status ---> traverse ; cycle ; no_cycle.
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%--------------------------------------------------
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main -->
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{ cycles(a, Cycles) },
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write_cycles(Cycles).
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%--------------------------------------------------
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:- pred arrow(node, node).
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:- mode arrow(in, in) is semidet.
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:- mode arrow(in, out) is nondet.
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:- mode arrow(out, out) is multi.
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arrow(a, b).
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arrow(b, c).
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arrow(c, c).
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arrow(a, d).
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arrow(d, a).
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%--------------------------------------------------
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:- pred cycles(node::in, list(list(node))::out) is det.
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cycles(N, Nodes) :-
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solutions(lambda([C::out] is nondet, (cycle(N, C))), Nodes).
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%--------------------------------------------------
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:- pred cycle(node::in, list(node)::out) is nondet.
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cycle(StartNode, NodeLs) :-
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cycle1(StartNode, StartNode, [StartNode], NodeLs, traverse).
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:- pred cycle1(node, node, list(node), list(node), status).
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:- mode cycle1(in, in, in, out, in) is nondet.
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cycle1(StartNode, CurrNode, NodeLs0, NodeLs, traverse) :-
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(arrow(CurrNode, AdjNode) ->
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((\+ list__member(AdjNode, NodeLs0)) ->
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Status1 = traverse
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;
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Status1 = cycle
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),
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NodeLs1 = [AdjNode | NodeLs0],
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cycle1(StartNode, AdjNode, NodeLs1, NodeLs, Status1)
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;
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cycle1(StartNode, StartNode, NodeLs0, NodeLs, no_cycle)
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).
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cycle1(StartNode, StartNode, NodeLs, NodeLs, cycle).
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%--------------------------------------------------
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:- pred node_to_char(node::in, char::out) is det.
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node_to_char(a, 'a').
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node_to_char(b, 'b').
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node_to_char(c, 'c').
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node_to_char(d, 'd').
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node_to_char(e, 'e').
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node_to_char(f, 'f').
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node_to_char(g, 'g').
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node_to_char(h, 'h').
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node_to_char(i, 'i').
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node_to_char(j, 'j').
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node_to_char(k, 'k').
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node_to_char(l, 'l').
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%--------------------------------------------------
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:- pred write_node(node::in, io__state::di, io__state::uo) is det.
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write_node(N) --> { node_to_char(N, C) }, io__write_char(C).
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%--------------------------------------------------
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:- pred write_nodes(list(node)::in, io__state::di, io__state::uo) is det.
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write_nodes(Nodes) --> write_nodes1(Nodes, yes).
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:- pred write_nodes1(list(node), bool, io__state, io__state).
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:- mode write_nodes1(in, in, di, uo) is det.
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write_nodes1([], yes) --> io__write_string("[]").
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write_nodes1([], no) --> io__write_string("]").
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write_nodes1([N|Ns], Start) -->
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( { Start = yes } -> io__write_string("[") ; { true }),
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write_node(N),
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( { Ns \= [] } -> io__write_string(", ") ; { true }),
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write_nodes1(Ns, no).
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%--------------------------------------------------
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:- pred write_cycles(list(list(node)), io__state, io__state).
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:- mode write_cycles(in, di, uo) is det.
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write_cycles(Nodes) --> write_cycles1(Nodes, yes), io__write_string("\n").
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:- pred write_cycles1(list(list(node)), bool, io__state, io__state).
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:- mode write_cycles1(in, in, di, uo) is det.
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write_cycles1([], yes) --> io__write_string("[]").
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write_cycles1([], no) --> io__write_string("]").
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write_cycles1([N|Ns], Start) -->
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( { Start = yes } -> io__write_string("[") ; { true }),
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write_nodes(N),
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( { Ns \= [] } -> io__write_string(", ") ; { true }),
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write_cycles1(Ns, no).
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%===========================================================================
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:- end_module cycles.
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