# To compute the determinant of a k by k matrix m.
 k > 0
 The matrix is corrupted. #

MODE R = REAL;
PROC det = (REF [,]R m)R: (INT k = 1 UPB m; 
(k /= 2 UPB m | print("not square"); GOTO hell);
(k = 1 | m[1,1]
| FOR j TO k DO (m[j,1] /= 0.0 |
   (j /= 1 | FOR n TO k DO
      R t = m[j, n]; m[j, n] := m[1, n]; m[1, n] := -t OD);
   GOTO zz) OD; 0 EXIT
zz: (
  R t = 1.0 / m[1,1];
  FOR i FROM 2 TO k DO REF []R q = m[i,]; R a = t*q[1];
     FOR r FROM 2 TO k DO q[r] -:= a*m[1, r] OD OD;
  m[1,1] * det(m[2:k, 2:k]))));

# To test: #
PROC t = ([,]R m)VOID: (INT k = 1UPB m;
  ([k,k]R z; FOR i TO k DO FOR j TO k DO z[i,j] := m[j,i] OD OD;
     print((det(LOC [k,k]R := m), " ", det(z), newline))));
t(((1, 0), (0, 1))); #1#
t(((1, 0, 0), (0, 1, 0), (0, 0, 1))); #1#
t(((2, 3), (5, 4))); #-7#
t(((0, 1, 0), (1, 0, 0), (0, 0, 1)));  #-1#
t(((3.3, 5.6, 4.8, 4.3),
   (5.6, 4.2, 6.7, 5.2),
   (7.6, 5.3, 6.6, 4.3),
   (2.6, 4.8, 4.9, 9.6))); #206.704#
t(((0, 2, 3), (0, 3, 6), (0, 5, 2))); #0#
hell: SKIP