Haskell data type for intervals

 A Numeric.Interval.Interval is a closed, convex set of floating point
 values.
 .
 This package does not control the rounding mode of the end points of the
 interval when using floating point arithmetic, so be aware that in order
 to get precise containment of the result, you will need to use an
 underlying type with both lower and upper bounds like CReal.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.