Collection of routines

Collection of small routines and constants, which are used across the whole package.

It's purpose is to serve as an "other" folder.

print_2d_array(array[, fmt, highlight, ...])	Print 1D and 2D arrays in the terminal.
volume(*args)	Computes volume.
angle(v1, v2[, radians])	Angle between two vectors.
absolute_to_relative(cell, absolute)	Compute relative coordinates with respect to the unit cell.
get_permutation(n, k)	Return array of index permutations
cell_from_param([a, b, c, alpha, beta, gamma])	Return cell from lattice parameters.
reciprocal_cell(cell)	Computes reciprocal cell.
span_orthonormal_set(vec)	Span orthonormal set of vectors.