问题描述
这个问题与一阶逻辑直接相关使用 prolog 为算术表达式创建术语.按照链接实现逻辑后,我遇到了 printauth/1
的输入格式问题.它目前的结果是 8-2+4* -3
,怎么可能得到类似 ((8-2)+(4* -3))
(注意它与 +(-(8,2),*(4,-3)))
不同.
我一直在尝试在 format/2
谓词中使用各种选项 (\k,\q) 但没有任何效果.即使我尝试了 write_canonical
和其他写谓词,仍然没有成功.
printterm(Term) :-算术表达式(Term, Expr), format("(~q)\n", [Expr]).%write_canonical(Expr).%write_term(Expr, [ignore_ops(true)]).%format("(~q)\n", [Expr]) .
电流输出:
?- printterm(plus((minus(8,2)),(times(4,3)))).(8-2+4*3)真的 .
预期输出:
?- printterm(plus((minus(8,2)),(times(4,3)))).((8-2)+(4*3))真的 .有可能实现吗?
您传递给 printterm
的术语:
plus((minus(8,2)),(times(4,3)))
通常写成:
plus(minus(8, 2), times(4, 3))
括号是不需要的,在阅读术语时确实会丢失.试试:
?- X = plus((minus(8,2)),(times(4,3))).
为了得到你想要的东西,你似乎真的需要对它进行编程.例如:
print_arithmetic_expression(E) :-短语(括号中的表达式(E),P),格式(~s~n",[P]).parenthesized_expression(E) -->atomic_expr(E),!.parenthesized_expression(E) -->{ expr_op(E, Op, A, B) },pexp(A),"", [Op], "",pexp(B).atomic_expr(E) -->{原子(E),格式(代码(C),〜w",[E])},C.expr_op(plus(A,B), 0'+, A, B).expr_op(minus(A,B), 0'-, A, B).expr_op(times(A,B), 0'*, A, B).pexp(E) -->atomic_expr(E),!.pexp(E) -->{ expr_op(E, Op, A, B) },(",pexp(A),"", [Op], "",pexp(B),)".
我明白了:
?- print_arithmetic_expression(plus(minus(8, 2), times(4, 3))).(8 - 2) + (4 * 3)真的.
This question is directly related to first order logic creating terms for arithmetic expressions using prolog. After implementing the logic as per the link I have issues with the formatting of the ourput for printauth/1
. It currently results as 8-2+4* -3
, how is it possible to get something like ((8-2)+(4* -3))
(notice its not the same as +(-(8,2),*(4,-3)))
.
I have been trying to using various options (\k,\q) in format/2
predicate but nothing works. even I tried write_canonical
and other write predicates, still no success.
printterm(Term) :- arithmetic_expression(Term, Expr), format("(~q)\n", [Expr]).
%write_canonical(Expr).
%write_term(Expr, [ignore_ops(true)]).
%format("(~q)\n", [Expr]) .
current output:
?- printterm(plus((minus(8,2)),(times(4,3)))).
(8-2+4*3)
true .
expected output:
?- printterm(plus((minus(8,2)),(times(4,3)))).
((8-2)+(4*3))
true .
Is it possible to achieve this?
The term you passed to your printterm
:
plus((minus(8,2)),(times(4,3)))
This is conventionally written as:
plus(minus(8, 2), times(4, 3))
The parentheses are not needed and are indeed lost when the term is read. Try:
?- X = plus((minus(8,2)),(times(4,3))).
To get what you want it seems you really need to program it. For example:
print_arithmetic_expression(E) :-
phrase(parenthesized_expression(E), P),
format("~s~n", [P]).
parenthesized_expression(E) -->
atomic_expr(E),
!.
parenthesized_expression(E) -->
{ expr_op(E, Op, A, B) },
pexp(A),
" ", [Op], " ",
pexp(B).
atomic_expr(E) -->
{ atomic(E),
format(codes(C), "~w", [E])
},
C.
expr_op(plus(A,B), 0'+, A, B).
expr_op(minus(A,B), 0'-, A, B).
expr_op(times(A,B), 0'*, A, B).
pexp(E) -->
atomic_expr(E),
!.
pexp(E) -->
{ expr_op(E, Op, A, B) },
"(",
pexp(A),
" ", [Op], " ",
pexp(B),
")".
I get:
?- print_arithmetic_expression(plus(minus(8, 2), times(4, 3))).
(8 - 2) + (4 * 3)
true.
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