We propose the addition of new functions to the C++0x standard library that provide floating-point operations (+, -, *, /, sqrt and fma) as well as conversion functions with directed rounding. This set of functions is necessary to provide efficient support for interval arithmetic and related computations, and they directly map to IEEE-754 specifications. These functions require special compiler support due to their "constexpr" nature. This document is submitted to the ISO/WG21 working group which standardizes the C++ language, under the document N2811 (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2811.pdf).