Look up tables mimic the evaluation of functions at different points. If a function is complicated or time taking to evaluate at any given point, one can use a Look Up Table, which contains the pre-evaluated sample points of the function. Later when an evaluation is requested, if the sample is directly found, the corresponding value is returned. On the other hand, if the value is not found, then an interpolation (most of the times it is linear to get better performance) of the values is performed to get an estimate of the actual function. In practice this gives a reasonable approximation of the function. Ofcourse when the values are out of bounds, then the last values are returned always.
This library currently supports linear interpolation in 1-D and 2-D only. Plan is to expand the interpolation and extrapolation options, along with generalizing the code to N-dimensions.