# ----------------------------------------
# File: Xiang/matrixAdd.py
# Title: Matrix multiplication. Xiang page 294 a
#A is:
#    5 4 1
#    0 -1 7
#B is:
#    2 -1 3
#    2 0 1
#    A + B is: 
#    7 3 4
#    2 -1 8
#---------------------------------------------
def initialize(X, N, M):  # make X[N][M]= [0,..0],..[0,..0]]
     for i in range(N):
        X.append([0]*M)
                      
def printMatrix(X):
    for i in X:     # i is X[0],X[1],.. 
        for j in i: # j is X[0][0],X[0][1],...
            print j,
        print       # endl after you print a line

def add(X,Y,Z):    # X[N][M] + Y[N][M] = Z[N][M]
    N = len(X)      # how many lines in X
    M = len(X[0])      # how many cols in X 
    for i in range(N):
        for j in range(M):
            Z[i][j] =  X[i][j] + Y[i][j]

def main():
    A = [[5,4,1],[0,-1,7]]   # A[2][3]
    B = [[2,-1,3],[2,0,1]]    # B[3][2]
    print "A is:"
    printMatrix(A)
    print "B is:"
    printMatrix(B)
    C=[]
    initialize(C,len(A),len(A[0]))  # initialize C[2][2] with 0
    add(A,B,C)
    print " A + B is: "
    printMatrix(C)
    
main()