### cofactor =====================================================================

Tags
----
scripting, JS, internal, treenode, general concept

Parameters
----------
m,i,j

General description
-------------------
Cofactor of a matrix component.
Let c be the cofactor matrix of matrix m, i.e. tranpose(c) = adj(m).
This function returns c[i,j].

###


Eval_cofactor = ->

  i = 0
  j = 0
  n = 0
  push(cadr(p1))
  Eval()
  p2 = pop()
  if (istensor(p2) && p2.tensor.ndim == 2 && p2.tensor.dim[0] == p2.tensor.dim[1])
    doNothing = 1
  else
    stop("cofactor: 1st arg: square matrix expected")
  n = p2.tensor.dim[0]
  push(caddr(p1))
  Eval()
  i = pop_integer()
  if (i < 1 || i > n)
    stop("cofactor: 2nd arg: row index expected")
  push(cadddr(p1))
  Eval()
  j = pop_integer()
  if (j < 1 || j > n)
    stop("cofactor: 3rd arg: column index expected")
  cofactor(p2, n, i - 1, j - 1)

cofactor = (p, n, row, col) ->
  i = 0
  j = 0
  for i in [0...n]
    for j in [0...n]
      if (i != row && j != col)
        push(p.tensor.elem[n * i + j])
  determinant(n - 1)
  if ((row + col) % 2)
    negate()