Haskell错误:解析输入`='时的错误 [英] Haskell Error: parse error on input `='

问题描述

规格

GHC 6.12.1

GHC 6.12.1

Mac OS X 10.6.4 x64

Mac OS X 10.6.4 x64

MacBook Pro

MacBook Pro

问题

我在使用 let 语法时遇到问题.以下代码拒绝编译:

I'm having trouble using let syntax. The following code refuses to compile:

module Main where

main = let x = 1
        y = 2
        z = 3
    in putStrLn $ "X = " ++ show x ++ "\nY = " ++ show y ++ "\nZ = " ++ show z

我尝试在 y = 2 和 z = 3 中进行制表.没有骰子.

I tried tabbing in y = 2 and z = 3 even more. No dice.

(不受欢迎的)解决方案

我要编译代码的唯一方法是要么

The only way I've gotten the code to compile is either

1. 用空格替换硬标签.
2. 用 where 子句替换 let 子句.

1. Replacing hard tabs with spaces.
2. Replacing the let clause with a where clause.

#haskell上的

推荐答案

Saizan解释说，let表达式中的赋值必须对齐，而不是 let 本身.只要任务排成一行，就可以使用硬标签或软标签.

Saizan on #haskell explains that the assignments in a let expression have to align, not let itself. As long as the assignments line up, it's okay to use hard tabs or soft tabs.

正确的代码:

module Main where

main = let
        x = 1
        y = 2
        z = 3
    in putStrLn $ "X = " ++ show x ++ "\nY = " ++ show y ++ "\nZ = " ++ show z

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