Haskell euclid算法两个整数的最大公约数

Question

Write a Haskell program egcd using Euclid's algorithm to to determine the greatest common divisor of two integers

我的程序:

eGCD :: Integer -> Integer -> (Integer, Integer, Integer)
eGCD 0 b = (b, 0, 1)
eGCD a b = let (g, s, t) = eGCD (b 'mod' a) a
       in (g, t - (b 'div' a) * s, s)

但在 WinGHCI 中运行时，出现错误:

 Prelude> :load C:\HaskellProject\egcd.hs

 C:\HaskellProject\egcd.hs:3:36: error:
    ? Syntax error on 'mod'
      Perhaps you intended to use TemplateHaskell or TemplateHaskellQuotes
    ? In the Template Haskell quotation 'mod'
    [1 of 1] Compiling Main             ( C:\HaskellProject\egcd.hs, interpreted )
 Failed, modules loaded: none.

Answer 1

要将函数用作中缀运算符，您需要用 ` 包围它们，而不是 ':

eGCD :: Integer -> Integer -> (Integer, Integer, Integer)
eGCD 0 b = (b, 0, 1)
eGCD a b = let (g, s, t) = eGCD (b `mod` a) a
       in (g, t - (b `div` a) * s, s)

' 用于字 rune 字。