Macro Library functioneval
A smattering of macros for evaluating complicated functions. Version 1.0 Oct 4 2009
fe_lpfnc(x,xarray,yarray,[periodic])
evals a linear piecewise function (connect-the-dots) from the provided
array of x and y values at the given x value.
requires x array to be in increasing order
If periodic=true, then xarray values define the domain of one period,
and if x is outside that domain, f(x) = f(x-p) will be used
domain: starting x <= x < last x, so make sure last x = x[0]+p