If you've installed a Haskell Platform since about 2012 on OS X, just run
uninstall-hs
and carefully read what it outputs. You'll need to run it again with the options it offers you. Run
uninstall-hs --help
for more options.
Below is my original answer, which will still work, but doesn't offer as many options and is a bit "ham fisted":
Warning: This script is extreme. It will remove even your custom config files for GHC and Cabal, and executables you've built that are still in ~/Library/Haskell or ~/.cabal. Use caution; review what it is about to do; have backups; caveat scriptor!
#!/bin/bash
set -x
sudo rm -rf /Library/Frameworks/GHC.framework
sudo rm -rf /Library/Frameworks/HaskellPlatform.framework
sudo rm -rf /Library/Haskell
rm -rf ~/.cabal
rm -rf ~/.ghc
rm -rf ~/Library/Haskell
find /usr/bin /usr/local/bin -type l | \
xargs -If sh -c '/bin/echo -n f /; readlink f' | \
egrep '//Library/(Haskell|Frameworks/(GHC|HaskellPlatform).framework)' | \
cut -f 1 -d ' ' > /tmp/hs-bin-links
sudo rm -f `cat /tmp/hs-bin-links`
You may want to add lines to save off and restore your config files like:
mv ~/.cabal/config /tmp/cabal-config 2>/dev/null || true
mv ~/.ghc/gchi.conf /tmp/ghci-config 2>/dev/null || true
and
mkdir ~/.cabal
mkdir ~/.ghc
cp /tmp/cabal-config ~/.cabal/config 2>/dev/null || true
cp /tmp/ghci-config ~/.ghc/gchi.conf 2>/dev/null || true
Bracket the rm lines with these. Though you may or may not want your old ~/.cabal/config if you are upgrading to newer stuff.
Note that this only deals with the current user's home directory. If you have multiple user accounts that all use Haskell, then the other accounts will need cleaning as well. (Repeat the lines involving ~.)
