...one of the most highly
regarded and expertly designed C++ library projects in the
world.

— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards

- Finding the Next Representable Value in a Specific Direction (nextafter)
- Finding the Next Greater Representable Value (float_next)
- Finding the Next Smaller Representable Value (float_prior)
- Calculating the Representation Distance Between Two Floating Point Values (ULP) float_distance
- Advancing a Floating Point Value by a Specific Representation Distance (ULP) float_advance

Unit of Least Precision or Unit in the Last Place is the gap between two different, but as close as possible, floating-point numbers.

Most decimal values, for example 0.1, cannot be exactly represented as floating-point values, but will be stored as the closest representable floating-point.

Functions are provided for finding adjacent greater and lesser floating-point values, and estimating the number of gaps between any two floating-point values.

The floating-point type FPT must have has a fixed number of bits in the representation.
The number of bits may set at runtime, but must be the same for all numbers.
For example, NTL::quad_float
type (fixed 128-bit representation) or NTL::RR
type (arbitrary but fixed decimal digits, default 150) but **not**
a type that extends the representation to provide an exact representation for
any number, for example XRC eXact
Real in C.