Question

我正在尝试将两个三角形比较两点和高度。

compare_tri( triangle ( point(X1,Y1), point(X2,Y2), H1),
    triangle( point(X3,Y3), point(X4,Y4), H2)) :-
    A1 is ((X2-X1)*(X2-X1)),
    B1 is ((Y2-Y1)*(Y2-Y1)),
    C1 is (A1+B1),
    D1 is (sqrt(C1)),
    S1 is (D1*H1),
    A2 is ((X4-X3)*(X4-X3)),
    B2 is ((Y4-Y3)*(Y4-Y3)),
    C2 is (A2+B2),
    D2 is (sqrt(C2)),
    S2 is (D2*H2),
    (  (S1 < S2)
    -> (S1 is 2), (S2 is 1)
    ;  (S2 is 2), (S1 is 1)
    ),
    write(S1), write('bigger than '), write(S2).

但是我收到错误消息'syntax operator：operator expected'

有什么问题？

Answer 1

triangle和下一个大括号之间必须没有空格：将triangle ( point(X1,Y1)更改为triangle( point(X1,Y1)，错误就会消失。

Answer 2

除了谢尔盖已经解决的语法错误之外，一般的建议是：尝试首先编写可重用的代码。它更容易调试，阅读，记忆......

triangle_area(triangle(point(X1,Y1), point(X2,Y2), H), S1) :-
 A1 is ((X2-X1)*(X2-X1)),
 B1 is ((Y2-Y1)*(Y2-Y1)),
 C1 is (A1+B1),
 D1 is (sqrt(C1)),
 S1 is (D1*H1).

compare_tri(T1,T2) :-
 triangle_area(T1,S1),
 triangle_area(T2,S2), etc etc...

比较Prolog中的三角形

2 个答案: