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npplus.pcwise module

A decorator to neatly write piecewise functions.

The decorator is an aid to writing functions of one variable x which have different algorithms in different domains of x:

@pcwise
def fun(x):
    def funlo(x):
        return 1. - x
    def funmid(x):
        return numpy.sin(x)
    def funhi(x):
        return x**2 - 1.
    return funlo, xa, funmid, xb, funhi

Defines fun(x) to be funlo(x) for x<xa, funmid(x) for xa<=x<xb, and funhi(x) for xb<=x. Any number of domains is allowed.

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pcwise(f)

Decorator to simplify creating f(x) with algorithm dependent on x.

Use the pcwise decorator like this:

@pcwise
def f(x):
    '''Return a function of a single real variable x.'''
    def f0(x):
        ...algorithm when       x < x1
    def f1(x):
        ...algorithm when x1 <= x < x2
    def f2(x):
        ...algorithm when x2 <= x < x3
    <and so on>
    return (f0, x1, f1, x2, f2, ...)

Any of the fN in the return value may be a string to raise a ValueError with that string for any points in that range.