如果您，将库放入 hs-source-dirs 目录中，通常不能使用 ghci 和 runhaskell ，特别是如果可执行文件本身有辅助模块的话。
什么是推荐的项目布局
runhaskell 假设您有一个 mylib 库，并且 mylib-commandline 和 mylib-server 可执行文件。
您可以使用 hs-source-dirs 用于库和每个可执行文件，以便每个文件都有自己的项目根目录，避免双重编译：
mylib /＃项目根目录
mylib.cabal
src /＃根目录该库
tests /
mylib-commandline /＃命令行实用程序的辅助工具+辅助程序模块
mylib-server /＃Web服务+辅助程序模块的根目录
$ b完整的目录布局：
mylib /＃项目根目录
mylib.cabal
src /＃库的根目录
Web /
Mylib.hs＃主库模块
Mylib /
ModuleA＃Mylib.ModuleA
ModuleB＃Mylib.ModuleB
tests /
...
mylib-commandline /＃命令行实用程序的根目录
Main.hs＃ 模块主要在哪里存根main = Web.Mylib.Commandline.Main.main
Web /
Mylib /
命令行/
Main.hs＃CLI入口点
Arguments.hs＃程序命令行参数解析器
mylib-server /＃Web服务的根目录
Server.hs＃module Main stub withmain = Web.Mylib.Server.Main.main
Web /
Mylib /
服务器/
Main.hs＃服务器入口点
参数.hs＃服务器命令行参数解析器
入口点文件
mylib-commandline / Main.hs看起来像这样：
module主要在
中导入限定的Web.Mylib.Server.Main作为MylibServer
main :: IO（）
main = MylibServer.main
您需要它们是因为
可执行文件必须在一个简单的Main。
您的
mylib.cabal看起来像这样：
library
hs-source-dirs：src
exposed-modules：
Web.Mylib
Web.Mylib.ModuleA
Web.Mylib.ModuleB
build-depends：
base> = 4&& < = 5
，[库的其他依赖关系]
可执行mylib-commandline
hs-source-dirs：mylib-commandline
main-is：Main .hs
other-modules：
Web.Mylib.Commandline.Main
Web.Mylib.Commandline.Arguments
build-depends：
ase> = 4& amp ;&安培; < = 5
，mylib
，[CLI的其他依赖性]
可执行文件mylib-server
hs-source-dirs：mylib-server
main-is：Server.hs
other-modules：
Web.Mylib.Server.Main
build-depends：
base> = 4&& < = 5
，mylib
，warp> = XX
，[服务器的其他依赖关系]
$cabal build将构建库和两个可执行文件，而不需要对库进行双重编译，因为每个文件都在它们自己的hs-source-dirs并且可执行文件依赖于库。
您仍然可以使用 runghc ，使用
-i开关来告诉它应该在哪里寻找模块（使用：作为分隔符）：runhaskell -isrc：mylib-commandline mylib-commandline / Main.hs
runhaskell -isrc：mylib-server mylib-server / Server.hs
方式，你可以有一个干净的布局，带有助手模块的可执行文件，并且所有东西都可以在
runhaskell/runghc和ghci中。为避免重复输入此标志，可以添加类似于
：set -isrc：mylib-commandline：mylib-server
添加到您的
.ghci文件中。
请注意，有时应该将您的代码拆分为不同的包，例如
mylib，mylib-commandline和mylib-server。If you declare a library + executable sections in a cabal file while avoiding double compilation of the library by putting the library into a
hs-source-dirsdirectory, you cannot usually run your project withghciandrunhaskellanymore, especially if the executables have helper modules themselves.What is a recommended project layout that
runhaskellLet's assume you have a mylib library, and mylib-commandline and mylib-server executables.
You use hs-source-dirs for the library and each executable so that each has their own project root, avoiding double compilation:
mylib/ # Project root
mylib.cabal
src/ # Root for the library
tests/
mylib-commandline/ # Root for the command line utility + helper modules
mylib-server/ # Root for the web service + helper modules
Full directory layout:
mylib/ # Project root
mylib.cabal
src/ # Root for the library
Web/
Mylib.hs # Main library module
Mylib/
ModuleA # Mylib.ModuleA
ModuleB # Mylib.ModuleB
tests/
...
mylib-commandline/ # Root for the command line utility
Main.hs # "module Main where" stub with "main = Web.Mylib.Commandline.Main.main"
Web/
Mylib/
Commandline/
Main.hs # CLI entry point
Arguments.hs # Programm command line arguments parser
mylib-server/ # Root for the web service
Server.hs # "module Main where" stub with "main = Web.Mylib.Server.Main.main"
Web/
Mylib/
Server/
Main.hs # Server entry point
Arguments.hs # Server command line arguments parser
The stub-like entry point file mylib-commandline/Main.hs looks like this:
module Main where
import qualified Web.Mylib.Server.Main as MylibServer
main :: IO ()
main = MylibServer.main
You need them because an executable must start on a module simply called Main.
Your mylib.cabal looks like this:
library
hs-source-dirs: src
exposed-modules:
Web.Mylib
Web.Mylib.ModuleA
Web.Mylib.ModuleB
build-depends:
base >= 4 && <= 5
, [other dependencies of the library]
executable mylib-commandline
hs-source-dirs: mylib-commandline
main-is: Main.hs
other-modules:
Web.Mylib.Commandline.Main
Web.Mylib.Commandline.Arguments
build-depends:
base >= 4 && <= 5
, mylib
, [other depencencies for the CLI]
executable mylib-server
hs-source-dirs: mylib-server
main-is: Server.hs
other-modules:
Web.Mylib.Server.Main
build-depends:
base >= 4 && <= 5
, mylib
, warp >= X.X
, [other dependencies for the server]
cabal build will build the library and the two executables without double compilation of the library, because each is in their own hs-source-dirs and the executables depend on the library.
You can still run the executables with runghc from your project root, using the -i switch to tell where it shall look for modules (using : as separator):
runhaskell -isrc:mylib-commandline mylib-commandline/Main.hs
runhaskell -isrc:mylib-server mylib-server/Server.hs
This way, you can have a clean layout, executables with helper modules, and everything still works with runhaskell/runghc and ghci. To avoid typing this flag repeatedly, you can add something similar to
:set -isrc:mylib-commandline:mylib-server
to your .ghci file.
Note that sometimes should split your code into separate packages, e.g. mylib, mylib-commandline and mylib-server.
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