Function: parmatrix
Section: programming/parallel
C-Name: parmatrix
Prototype: LLVVJ
Description:
  (small,small,,,closure):vec    parmatrix($1, $2, $5)
Help: parmatrix(m,n,i,j,expr): as matrix(m,n,i,j,expr) but the evaluations of expr are
 done in parallel.
Doc: As \kbd{matrix(m,n,i,j,expr)} but the evaluations of \kbd{expr} are done in
 parallel. The expression \kbd{expr} must not access global variables or
 variables declared with \kbd{local()}, and must be free of side effects.

Function: _parmatrix_worker
Section: programming/internals
C-Name: parmatrix_worker
Prototype: GGG
Help: _parmatrix_worker(i,j,C): evaluate the closure C on i,j
