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add occurs_check flag (#309)

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This commit is contained in:
Mark Thom
2021-02-28 10:41:32 -07:00
parent 8e6a89b279
commit a367812348
6 changed files with 210 additions and 141 deletions
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8
src/lib/builtins.pl
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@@ -133,6 +133,10 @@ current_prolog_flag(Flag, Value) :- Flag == double_quotes, !, '$get_double_quote
current_prolog_flag(double_quotes, Value) :- '$get_double_quotes'(Value).
current_prolog_flag(Flag, _) :- Flag == max_integer, !, '$fail'.
current_prolog_flag(Flag, _) :- Flag == min_integer, !, '$fail'.
current_prolog_flag(Flag, OccursCheckEnabled) :-
Flag == occurs_check,
!,
'$is_sto_enabled'(OccursCheckEnabled).
current_prolog_flag(Flag, _) :-
atom(Flag),
throw(error(domain_error(prolog_flag, Flag), current_prolog_flag/2)). % 8.17.2.3 b
@@ -163,6 +167,10 @@ set_prolog_flag(double_quotes, atom) :-
!, '$set_double_quotes'(atom). % 7.11.2.5, list of char codes (UTF8).
set_prolog_flag(double_quotes, codes) :-
!, '$set_double_quotes'(codes).
set_prolog_flag(occurs_check, true) :-
!, '$set_sto_as_unify'.
set_prolog_flag(occurs_check, false) :-
!, '$set_nsto_as_unify'.
set_prolog_flag(double_quotes, Value) :-
throw(error(domain_error(flag_value, double_quotes + Value),
set_prolog_flag/2)). % 8.17.1.3 e