Math::LinearCombination is a module for representing mathematical linear combinations of variables, i.e. expressions of the format a1 * x1 + a2 * x2 + ... + an * xn with x1, x2, ..., xn variables, and a1, a2, ..., an numerical coefficients. Evaluation and manipulation of linear combinations is also supported. The numerical coefficients a_i and variables x_i are stored as pairs in an internal data structure and should not be manipulated directly. All access and manipulation should be performed through the methods.