rishi/scryer-prolog
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ENHANCED: Delay toplevel output until after the goal succeeds.

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This is to accommodate goals that are used for their side-effects,
when we are interested in their output.

Examples:

    ?- portray_clause((a :- a)).
    a :-
            a.
       true
    ;  false.

    ?- format("hello~w~n", [!]).
    hello!
       true
    ;  false.
This commit is contained in:
Markus Triska
2020-04-19 01:28:50 +02:00
parent 9daf290432
commit 075ca78dd2
1 changed files with 19 additions and 6 deletions
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25
src/prolog/toplevel.pl
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@@ -46,16 +46,24 @@ instruction_match(Term, VarList) :-
submit_query_and_print_results(Term, VarList) submit_query_and_print_results(Term, VarList)
). ).
:- use_module(library(iso_ext)).
% auxiliary predicates, so that using them in setup_call_cleanup/3 works
get_b_value(B) :- '$get_b_value'(B).
clear_attribute_goals :- '$clear_attribute_goals'.
submit_query_and_print_results(Term0, VarList) :- submit_query_and_print_results(Term0, VarList) :-
( expand_goals(Term0, Term) -> true ( expand_goals(Term0, Term) -> true
; Term0 = Term ; Term0 = Term
), ),
( '$get_b_value'(B), write(' '), call(Term), write_eqs_and_read_input(B, VarList), setup_call_cleanup(bb_put('$first_answer', true),
! ( get_b_value(B), call(Term), write_eqs_and_read_input(B, VarList),
% clear attribute goal lists, which may be populated by !
% copy_term/3 prior to failure. ; % clear attribute goal lists, which may be populated by
; '$clear_attribute_goals', write('false.'), nl % copy_term/3 prior to failure.
). clear_attribute_goals, write('false.'), nl
),
bb_put('$first_answer', false)).
needs_bracketing(Value, Op) :- needs_bracketing(Value, Op) :-
catch((functor(Value, F, _), catch((functor(Value, F, _),
@@ -132,6 +140,11 @@ write_eqs_and_read_input(B, VarList) :-
sort(NewVarList, SortedVarList), sort(NewVarList, SortedVarList),
'$get_b_value'(B0), '$get_b_value'(B0),
gather_goals(SortedVarList, SortedVarList, Goals), gather_goals(SortedVarList, SortedVarList, Goals),
( bb_get('$first_answer', true) ->
write(' '),
bb_put('$first_answer', false)
; true
),
( B0 == B -> ( B0 == B ->
( Goals == [] -> ( Goals == [] ->
write('true.'), nl write('true.'), nl