function [ y ] = forward_substitutions( L, b )
% FORWARD_SUBSTITUTIONS solve the linear system L y = b by means of the
% forward subsitutions algorithm; L must be a lower triangular matrix
%  [ y ] = forward_substitutions( L, b )
%  Inputs: L = lower triangular matrix (square matrix)
%          b = vector (right hand side of the linear system)
%  Output: y = solution vector (column vector)
%


return