# ----------------------------------------
# File: Xiang/matrixMult.py
# Title: Matrix multiplication. Xiang page 282
#   A is:
#   3 2 5
#   1 -1 2
#   B is:
#   -1 0
#   2 3
#   1 2
#    A * B is: 
#   6 16
#   -1 1
#---------------------------------------------
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 mult(X,Y,Z):    # X[N][M] x Y[M][K] = Z[N][K]
    N = len(X)      # how many lines in X
    M = len(Y)      # how many lines in Y (same as cols in X)
    K = len(Y[0])   # how many cols in Y
    for i in range(N):
        for j in range(K):
            for k in range(M):
                Z[i][j] =  X[i][k] * Y[k][j] + Z[i][j]

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