The "Numeric.FastMath" module brings into scope many unsafe 'RULES' for
'Float's and 'Double's that can greatly improve run time performance.
It is roughly equivalent to gcc's '-ffast-math' compiler flag.
Optimisation (at least '-O1') must be enabled for any 'RULES' to take effect.
These rules are unsafe because they don't strictly adhere to the IEEE-754
regulations and may subtly change the results of your numeric computations.
See the <http://github.com/liyang/fast-math/ README> on github for more