Helper Functions for SCA Alignment (calign, and misc)

The helper functions and classes below play an important role in all SCA alignment algorithms in LingPy (List2012b). They are implemented both in pure Python and in Cython (only supported for Python 3), in order to allow for faster implementations of the core alignment functions. Instead of using these functions directly, we recommend to use the more general functions which you can find in the pairwise and the multiple module of LingPy, and which are based on the helper functions we list below.