functions:equation-solver

example

 The following macro, INVERSE.PCM, will find the inverse of a square
 matrix. If you have a square matrix M, you could find it's inverse,
 INV_M, with the command: @INVERSE M

 if ( vlen(?1)[1] "NE" vlen(?1)[2] ) then
   display `input matrix must be square'
   return
 endif
 n = vlen(?1)[1]
 ! identity(n) is the identity matrix of order n
 do k = [1:n]
  inv_m[1:n,k] = gaussj(?1,identity(n)[1:n,k])
 enddo