Factorial procedure

factorial.proc

  # Calculate the factorial of a number using
  # a recursive procedure.
  # A demonstration of the limitations of Praat
  # procedures (and of possible workarounds).
  #
  # Author: José Joaquín Atria
  
  procedure factorial: .n
    # Cannot use an inline if here
    if !variableExists("factorial.level")
      .level = 1
    else
      .level += 1
    endif
    .n[.level] = .n

    if !.n
      .a[.level] = 1
    else
      @factorial: .n-1
      .a[.level] = .n[.level] * factorial.a[.level+1]
    endif
    .level -= 1
  endproc