为什么这段代码无法运行? ECLiPSe-clp中的“语法错误:预期的后缀/中缀运算符”错误是什么？

Question

当我想在ECLiPSe-CLP中运行这段代码时，我得到以下错误

Error:
string stream 27: syntax error: postfix/infix operator expected

|     4 $= X^2 + Y^2,   (Error Mark is under '=')
|           

代码：

circles(X, Y) :-
    4 $= X^2 + Y^2,
    4 $= (X - 1)^2 + (Y - 1)^2,
    X $>= Y.

Answer 1

$=/2操作符/谓词是一个库谓词。你正在加载定义它的库吗？例如。

[eclipse 12]: lib(ic).
...
Yes (0.12s cpu)

[eclipse 13]: [user].
circles(X, Y) :-
     4 $= X^2 + Y^2,
    4 $= (X - 1)^2 + (Y - 1)^2,
     X $>= Y.
 ^Dtty        compiled 4024 bytes in 0.00 seconds

Yes (0.00s cpu)

[eclipse 14]: circles(X, Y).

X = X{-1.0000000000000004 .. 2.0000000000000004}
Y = Y{-1.0000000000000004 .. 2.0000000000000004}

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