Regularised functions

There are functions in mathematics which look innocent from an analytic viewpoint but that give birth to a number of computational issues once implemented numerically. Some of them are famous, like the sign function or the absolute value, some other are less known and do not contain apparent traps such as power (i.e. exponent of a function).

PINS redefines an approximations of those functions in order they are smooth and differentiable up to the second derivatives, at leats.