C# now has biginteger, but what about support for arbitrary precision floating point numbers

Now that biginteger (System.Numerics.BigInteger) support has been added in C# 4.0, it would be nice if arbitrary precision floating point/fixed 开发者_运维知识库point was also possible. Are there any good (preferably free) third party libraries that offer efficient arbitrary precision floating/fixed point capabilities?

Arbitrary precision floating- and fixed-point numbers can easily be coded as ratios of BigIntegers. I don't know of any off-the-shelf libraries for them but then I don't know much about C#.