Installation error of libxml-sax

[Peng Yu]

I got the following errors. Does anybody know how to fix it? Thanks.

~$ cabal install libxml-sax
Resolving dependencies...
Configuring libxml-sax-0.7.5...
Failed to install libxml-sax-0.7.5
Last 10 lines of the build log (
/Users/pengy/.cabal/logs/libxml-sax-0.7.5.log ):
Configuring libxml-sax-0.7.5...
setup-Cabal-1.18.1.4-x86_64-osx-ghc-7.8.3: The program pkg-config version
>=0.9.0 is required but it could not be found.
cabal: Error: some packages failed to install:
libxml-sax-0.7.5 failed during the configure step. The exception was:
ExitFailure 1

-- 
Regards,
Peng