pyswip中的prolog代码不工作

Question

我的问题与这个问题有关。

我希望下面的prolog代码嵌入到python程序中：

myEquation(A, B, C):- 
    var(A),number(B),number(C) -> A is B+C;
    var(B),number(A),number(C) -> B is A-C;
    var(C),number(A),number(B) -> C is A-B;
    A =:= B + C.

我安装了pyswip包并尝试了以下代码：

from pyswip import Prolog
prolog = Prolog()
prolog.assertz("myEquation(A, B, C):- var(A),number(B),number(C) -> A is B+C; var(B),number(A),number(C) -> B is A-C; var(C),number(A),number(B) -> C is A-B; A =:= B + C.")
prolog.assertz("myEquation(3,1,C).")

但这给了我一个错误：

ERROR: Syntax error: Operator priority clash
ERROR: assertz((myEquation(A, B, C):- var(A),number(B),number(C) -> A is B+C; var(B),number(A),number(C) -> B is A-C; var(C),number(A),number(B) -> C is A-B; A
ERROR: ** here **
ERROR:  =:= B + C.)). 
Traceback (most recent call last):
  File "prologpy.py", line 4, in <module>
    prolog.assertz("myEquation(A, B, C):- var(A),number(B),number(C) -> A is B+C; var(B),number(A),number(C) -> B is A-C; var(C),number(A),number(B) -> C is A-B; A =:= B + C.")
  File "/home/cardio/.local/lib/python3.5/site-packages/pyswip/prolog.py", line 140, in assertz
    next(cls.query(assertion.join(["assertz((", "))."]), catcherrors=catcherrors))
  File "/home/cardio/.local/lib/python3.5/site-packages/pyswip/prolog.py", line 127, in __call__
    "Returned: '", str(term), "'."]))
pyswip.prolog.PrologError: Caused by: 'assertz((myEquation(A, B, C):- var(A),number(B),number(C) -> A is B+C; var(B),number(A),number(C) -> B is A-C; var(C),number(A),number(B) -> C is A-B; A =:= B + C.)).'. Returned: 'error(syntax_error(operator_clash), string(b'assertz((myEquation(A, B, C):- var(A),number(B),number(C) -> A is B+C; var(B),number(A),number(C) -> B is A-C; var(C),number(A),number(B) -> C is A-B; A =:= B + C.)). ', 152))'.

我怎样才能解决这个问题。我还可以使用其他一些与prolog相关的python包，比如列在这里。

Answer 1

谓词定义末尾的.太多了。把它处理掉。

例如，这是正确的：

?- assertz((foo :- bar)).

但这是不对的：

?- assertz((foo :- bar.)).

如果您阅读了示例提供吡咯烷酮，您应该注意到上面的本机Prolog代码转换为：

from pyswip import Prolog
prolog = Prolog()
prolog.assertz("(foo :- bar)")

而不是你写的，

prolog.assertz("(foo :- bar.)")