运行并编译“Hello，World！”在Haskell

Question

我是Haskell的新手，在运行以下代码时遇到问题：

module Main (
main
) where 
main = putStrLn "Hello, world!"

SublimeHaskell尝试使用以下命令编译和运行上面的代码

runhaskell hello.hs

，它返回错误

hello.o: getModificationTime: invalid argument (The system cannot find the file specified.)

我还尝试使用以下命令运行它

ghc --make hello.hs

带着同样的错误。当我尝试在使用命令行运行之前手动编译代码时

ghc -c hello.hs

我得到一个不同的错误：

CreateDirectory ".": invalid argument (Cannot create a file when that file already exists.)

另一方面，我可以通过REPL运行程序而不会出现问题：

ghci
GHCi, version 8.0.1: http://www.haskel.org/ghc/  :? for help
Prelude> putStrLn "Hello, world!"
Hello, world!

如果相关，我使用的是Windows7，并且我使用Haskell平台安装程序安装了GHC。

*edit使用-v标志运行上述命令会产生以下结果：

ghc -v hello.hs

Glasgow Haskell Compiler, Version 8.0.1, stage 2 booted by GHC version     7.10.2
Using binary package database: C:\Program Files\Haskell      Platform\8.0.1\lib\package.conf.d\package.cache
loading package database C:\Program Files\Haskell    Platform\8.0.1\lib\package.conf.d
wired-in package ghc-prim mapped to ghc-prim-0.5.0.0
wired-in package integer-gmp mapped to integer-gmp-1.0.0.1
wired-in package base mapped to base-4.9.0.0
wired-in package rts mapped to rts
wired-in package template-haskell mapped to template-haskell-2.11.0.0
wired-in package ghc mapped to ghc-8.0.1
wired-in package dph-seq not found.
wired-in package dph-par not found.
Hsc static flags:
loading package database C:\Program Files\Haskell     Platform\8.0.1\lib\package.conf.d
wired-in package ghc-prim mapped to ghc-prim-0.5.0.0
wired-in package integer-gmp mapped to integer-gmp-1.0.0.1
wired-in package base mapped to base-4.9.0.0
wired-in package rts mapped to rts-1.0
wired-in package template-haskell mapped to template-haskell-2.11.0.0
wired-in package ghc mapped to ghc-8.0.1
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Chasing dependencies:
Chasing modules from: *hello.hs
*** Deleting temp files:
Deleting:
*** Deleting temp dirs:
Deleting:
hello.o: getModificationTime: invalid argument (The system cannot find the file specified.)

ghc -c -v hello.hs

Glasgow Haskell Compiler, Version 8.0.1, stage 2 booted by GHC version 7.10.2
Using binary package database: C:\Program Files\Haskell     Platform\8.0.1\lib\package.conf.d\package.cache
loading package database C:\Program Files\Haskell    Platform\8.0.1\lib\package.conf.d
wired-in package ghc-prim mapped to ghc-prim-0.5.0.0
wired-in package integer-gmp mapped to integer-gmp-1.0.0.1
wired-in package base mapped to base-4.9.0.0
wired-in package rts mapped to rts
wired-in package template-haskell mapped to template-haskell-2.11.0.0
wired-in package ghc mapped to ghc-8.0.1
wired-in package dph-seq not found.
wired-in package dph-par not found.
Hsc static flags:
*** Checking old interface for Main:
*** Parser [Main]:
!!! Parser [Main]: finished in 0.00 milliseconds, allocated 0.067 megabytes
*** Renamer/typechecker [Main]:
!!! Renamer/typechecker [Main]: finished in 46.80 milliseconds, allocated  15.720 megabytes
*** Desugar [Main]:
Result size of Desugar (after optimization)
= {terms: 13, types: 6, coercions: 0}
!!! Desugar [Main]: finished in 0.00 milliseconds, allocated 0.204 megabytes
*** Simplifier [Main]:
Result size of Simplifier iteration=1
= {terms: 17, types: 8, coercions: 0}
Result size of Simplifier = {terms: 17, types: 8, coercions: 0}
!!! Simplifier [Main]: finished in 0.00 milliseconds, allocated 0.171  megabytes
*** CoreTidy [Main]:
Result size of Tidy Core = {terms: 17, types: 8, coercions: 0}
!!! CoreTidy [Main]: finished in 0.00 milliseconds, allocated 2.558  megabytes
*** Deleting temp files:
Deleting:
*** Deleting temp dirs:
Deleting:
CreateDirectory ".": invalid argument (Cannot create a file when that file already exists.)

环顾四周，似乎列出的两个未找到的包(dph-seq和dph-par)已被弃用。

Answer 1

GHC要求文件的名称与模块的名称相同，以便对其进行编译。但是，无论文件名如何，任何模块都可以加载到GHCi中。这就是为什么repl可以工作，而编译不能。

因此，在您的示例中，应将文件重命名为Main.hs