方案:重载内置程序，一般重载 [英] Scheme: overload built-in procedures, general overloading

问题描述

更具体地说，你能重载内置的 Scheme 程序显示吗?

More specifically, can you overload the built-in Scheme procedure display?

更一般地说，如何在 Scheme 中重载任何过程?

More generally, how can you overload any procedure in Scheme?

推荐答案

Scheme 没有像 Java/C++ 那样基于类型的重载，它是动态类型的，所以没有意义.

Scheme doesn't have overloading based on types a`la Java/C++, it's dynamically typed so it wouldn't make sense.

你可以做一些事情:

您可以根据参数的结构进行重载:

You can overload based on the structure of the arguments:

(define overload1
    (case-lambda
        ((x y) (+ x y))
        ((x y z) (+ (- x y) z))))

这并没有真正帮助你，因为 display 无论如何都只会接受一个参数.

This doesn't really help you though since display is only going to take one argument no matter what.

(define (overload-kinda x)
    (cond
        ((list? x) (do-list x))
        ((symbol? x) (do-sym x))
        ;etc
        ))

这很棘手，但有时是必要的.

Which is hacky but sometimes necessary.

我通常的方法是高阶函数和情况 lambda

My usual approach is higher order functions and the case lambda

(define my-display
    (case-lambda
        ((x) (display x))
        ((x f) (display (f x)))))

现在，如果我们需要特殊处理来显示任何内容，我们会传入一个函数来渲染它.

Now if we need special treatment for displaying anything we pass in a function to render it.

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