/* matblock.mac */
/* (C) Kenrou Adachi , 2004/2/25 */
/* version 0.1 */

matblock(Mat,i1,i2,j1,j2) := block([_A, _m, _n, _i, _j],
    _m : i2 - i1, _n : j2 - j1,
    _A : zeromatrix(_m + 1, _n + 1),
    for _i : 1 thru _m + 1 do
        for _j : 1 thru _n + 1 do
            _A[_i][_j] : Mat[i1 + _i - 1][j1 + _j - 1],
    _A
)$

matreplace(Mat1,Mat2,i1,i2,j1,j2) := block([_A, _m, _n, _i, _j],
    _m : i2 - i1, _n : j2 - j1,
    _A : copymatrix(Mat1),
    for _i : 1 thru _m + 1 do
        for _j : 1 thru _n + 1 do
            _A[i1 + _i - 1][j1 + _j - 1] : Mat2[_i][_j],
    _A
)$

/* examples */
/*
(C1) A : matrix([q,w,e,r,t],[y,u,i,o,p],[a,s,d,f,g],[h,j,k,l,z],[x,c,v,b,n]);
                               [ q  w  e  r  t ]
                               [               ]
                               [ y  u  i  o  p ]
                               [               ]
(D1)                           [ a  s  d  f  g ]
                               [               ]
                               [ h  j  k  l  z ]
                               [               ]
                               [ x  c  v  b  n ]
(C2) load("./matblock.mac");                                                 
(D2)                            ./matblock.mac
(C3) matblock(A, 2,4,2,4);  
                                  [ u  i  o ]
                                  [         ]
(D3)                              [ s  d  f ]
                                  [         ]
                                  [ j  k  l ]
(C4) matblock(A, 2,2,2,2);
(D4)                                 [ u ]
(C5) matblock(A,2,5,3,4);
                                   [ i  o ]
                                   [      ]
                                   [ d  f ]
(D5)                               [      ]
                                   [ k  l ]
                                   [      ]
                                   [ v  b ]
(C6) B : matrix([1,2,3],[4,5,6],[7,8,9]);
                                  [ 1  2  3 ]
                                  [         ]
(D6)                              [ 4  5  6 ]
                                  [         ]
                                  [ 7  8  9 ]
(C7) B : matrix([1,2],[3,4]);
                                   [ 1  2 ]
(D7)                               [      ]
                                   [ 3  4 ]
(C8) matreplace(A,B,1,2,1,2);
                               [ 1  2  e  r  t ]
                               [               ]
                               [ 3  4  i  o  p ]
                               [               ]
(D8)                           [ a  s  d  f  g ]
                               [               ]
                               [ h  j  k  l  z ]
                               [               ]
                               [ x  c  v  b  n ]
(C9) C : matrix([1,2,3],[4,5,6],[7,8,9]);
                                  [ 1  2  3 ]
                                  [         ]
(D9)                              [ 4  5  6 ]
                                  [         ]
                                  [ 7  8  9 ]
(C10) matreplace(A,C,2,4,2,4);
                               [ q  w  e  r  t ]
                               [               ]
                               [ y  1  2  3  p ]
                               [               ]
(D10)                          [ a  4  5  6  g ]
                               [               ]
                               [ h  7  8  9  z ]
                               [               ]
                               [ x  c  v  b  n ]
*/
/* end of matblock.mac */