哈希克尔方程求解实数 [英] Haskell equation solving in the real numbers

问题描述

我刚刚开始玩GHCi。我发现列表生成器基本上可以解决给定集合中的方程：

  Prelude> [x | x < -  [1..20]，x ^ 2 == 4] 
 [2] 
  

（如预期的那样，只找到一个根）

现在，为什么我不能用解决方案求解方程式，因为解决方案是包含在指定范围内？

  [x | x < -  [0.1,0.2..2.0]，x * 4 == 2] 
  

编辑：对不起，我的意思当然是 0.1 。

/ p>

解决方案

正如其他人所提到的，这不是解决方程式的有效方法，但可以用比率来完成。

  Prelude> ：m + Data.Ratio 
 Prelude Data.Ratio> [x | x < -  [1％10,2％10..2]，x * 4 == 2] 
 [1％2] 
  

$ b

阅读 x％y 为 x除以y 。

I've just started playing with GHCi. I see that list generators basically solve an equation within a given set:

Prelude> [x | x <- [1..20], x^2 == 4]
[2]

(finds only one root, as expected)

Now, why can't I solve equations with results in ℝ, given that the solution is included in the specified range?

[x | x <- [0.1,0.2..2.0], x*4 == 2]

How can I solve such equations within real numbers set?

Edit: Sorry, I meant 0.1, of course.

解决方案

As others have mentioned, this is not an efficient way to solve equations, but it can be done with ratios.

Prelude> :m +Data.Ratio 
Prelude Data.Ratio> [x|x<-[1%10, 2%10..2], x*4 == 2]
[1 % 2]

Read x % y as x divided by y.

这篇关于哈希克尔方程求解实数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！