Use ideas from the C++ numerics library

[wolfram77]

Consider the following enhancements. Include any functions that have not already been mentioned.

Basic operations

• fmod
• remainder

Floating point manipulation functions

• copysign*

Classification and comparison

• fpclassify*
• isnormal*
• signbit*
• isunordered*

Factor operations

• gcd
• lcm

Interpolation operations

• midpoint*
• lerp

[wolfram77]

About copysign()

The copysign() function can be useful in situations where you want to preserve the magnitude of a number but change its sign based on another value. For example, it can be used in mathematical operations where the result should be positive or negative depending on the input, such as finding the distance between two points, or in physics simulations where the direction of movement is determined by the sign of the velocity.

It can also be useful in financial applications where the sign of a value represents the direction of a trade (positive for a buy, negative for a sell) but the magnitude represents the quantity of the trade, and you want to change the direction of the trade but preserve the quantity. Another use case can be in Computer Graphics when you want to keep the magnitude of a value (e.g. length) but change its sign based on the orientation of a surface or object.