Usage:
cabal sandbox init
cabal install --dependencies-only
cabal build
time bash -c "cat file.txt | ./dist/build/wc-hs/wc-hs"
Following a series of tutorial posts by Rodney Lopes Gomes on how to create a simple clone of wc util. The final solution is still not perfect and could be optimized more. It does run slower than original wc on my Mac OS X for a large file (with about 2000000 lines), although in the blog post it is said that this small program runs faster in some cases.
Links to the posts: