编译一款文档生成程序－haddock

git clone https://github.com/haskell/haddock
cd haddock
cabal sandbox init
cabal sandbox add-source haddock-library
cabal sandbox add-source haddock-api
cabal sandbox add-source haddock-test
cabal install

~/haddock/.cabal-sandbox/bin/haddock或
~/haddock/dist/dist-sandbox-f4d3fb08/build/haddock/haddock就是可执行文件。
你可把~/haddock/.cabal-sandbox/bin/添加到环境变量。

项目地址：https://github.com/haskell/haddock,
Haddock User Guide: https://www.haskell.org/haddock/doc/html/index.html