How to install Haskell on Mac OS

Try using the Mac version of the Haskell Platform, I don't have a Mac to try it out but my hope is that cabal will work out-of-the-box in the Haskell Platform.

brew install ghc cabal-install

If you prefer homebrew.

Note: (Edited to add) Homebrew may have an older (or newer) version of ghc than the Haskell Platform download for OSX, and there might be other differences. You can check the release notes here for the version included in Haskell Platform, as well as other information of interest. brew info ghc cabal-install will give you up to date information about Homebrew's versions.

Note: The last time I did this, I just installed haskell-stack instead, as described in Filippo's answer.

To install the "Haskell Stack" binaries via homebrew:

brew install haskell-stack

---

EDIT: Below my original answer

If you want to install the Haskell Platform binaries via homebrew:

brew install cask
brew cask install haskell-platform

cabal install cabal-install