Taken quite directly from the Peyton Jones/Lester paper.
\begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module CoreFVs (
exprFreeVars, -- CoreExpr -> VarSet -- Find all locally-defined free Ids or tyvars
exprsFreeVars, -- [CoreExpr] -> VarSet