我如何在 Idris 中使用分数？

Question

当我尝试用一个整数除以另一个整数时，我收到以下消息：

Idris> 6 / 8
Can't find implementation for Fractional Integer

这到底是什么意思？ 如何在 Idris 中使用有理数？

Answer 1

Idris does not have a built-in type for rational numbers. The error message you are seeing means that the (/) function, which is a method of the Fractional 接口，要求其参数是实现该接口的类型；然而，目前唯一实现 Fractional 接口的类型是 Double:

Idris> :doc Fractional
Interface Fractional

Parameters:
    ty

Constraints:
    Num ty

Methods:
    (/) : Fractional ty => ty -> ty -> ty

        infixl 9

        The function is Total
    recip : Fractional ty => ty -> ty


        The function is Total
Implementations:
    Fractional Double

我如何在 Idris 中使用分数？

How can I use fractions in Idris?

fractions

idris