SWI Prolog 中是否有类似匿名谓词的东西? [英] Is there something like anonymous predicates in SWI Prolog?

问题描述

我可以在 SWI Prolog 中定义一个匿名谓词，将它绑定到一个变量，然后再调用它吗?像这样:

Can I define an anonymous predicate in SWI Prolog, bind it to a variable, and call it later? Something like this:

?- F = {(X, Y) :- Y is 2 * X}, call(F, 2.0, Y).

推荐答案

或者，在 SWI-Prolog 中，您可以使用 图书馆(yall).它可以自动加载，因此您无需导入任何内容:

Alternatively, in SWI-Prolog, you can use library(yall). It can be autoloaded so you don't need to import anything:

?- F = [X, Y]>>( Y is 2*X ), call(F, 2.0, Y).
F = [X, 4.0]>>(4.0 is 2*X),
Y = 4.0.

我认为在一般情况下，最好为调用 lambda 的结果使用一个新变量:

I think that in the general case it would be better to use a new variable for the result of calling the lambda:

?- F = [X, Y]>>( Y is 2*X ), call(F, 2.0, R).
F = [X, Y]>>(Y is 2*X),
R = 4.0.

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