Easy OSX GHC version switching and management via ghc-dot-app: https://github.com/ghcformacosx/ghc-dot-app

.bashrc

export CABALPATH=$HOME/.cabal
export PATH=$PATH:$CABALPATH/bin

function switchghc() {
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/cabal" /usr/local/bin/cabal
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/ghc-$@" /usr/local/bin/ghc
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/ghc-pkg-$@" /usr/local/bin/ghc-pkg
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/ghci-$@" /usr/local/bin/ghci
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/haddock-ghc-$@" /usr/local/bin/haddock
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/hp2ps" /usr/local/bin/hp2ps
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/hpc" /usr/local/bin/hpc
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/hsc2hs" /usr/local/bin/hsc2hs
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/runghc-$@" /usr/local/bin/runghc
  ln -sf "/usr/local/lib/ghc-$@.app/Contents/bin/runhaskell" /usr/local/bin/runhaskell

  printf "GHC et al changed to version $@\n"
}

install-ghc.sh

#!/bin/bash

rm -rf /usr/local/lib/ghc-7.8.2.app
curl -Lo /tmp/ghc-7.8.2.zip https://github.com/etrepum/ghc-dot-app/releases/download/v7.8.2-r8/ghc-7.8.2-r8.zip
unzip -q /tmp/ghc-7.8.2.zip -d /usr/local/lib/
chmod -R 0755 /usr/local/lib/ghc-7.8.2.app

rm -rf /usr/local/lib/ghc-7.8.3.app
curl -Lo /tmp/ghc-7.8.3.zip https://github.com/etrepum/ghc-dot-app/releases/download/v7.8.3-r0/ghc-7.8.3-r0.zip
unzip -q /tmp/ghc-7.8.3.zip -d /usr/local/lib/
chmod -R 0755 /usr/local/lib/ghc-7.8.3.app

usage.sh

$ switchghc 7.8.3
GHC et al changed to v7.8.3
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.3
$ switchghc 7.8.2
GHC et al changed to v7.8.2
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.2