Function: math-compute-nper

math-compute-nper is a byte-compiled function defined in calc-fin.el.gz.

Signature

(math-compute-nper RATE PMT AMOUNT LUMP BFLAG)

Source Code

;; Defined in /usr/src/emacs/lisp/calc/calc-fin.el.gz
(defun math-compute-nper (rate pmt amount lump bflag)
  (and lump (math-zerop lump)
       (setq lump nil))
  (and lump (math-zerop pmt)
       (setq amount lump
	     lump nil
	     bflag 'l))
  (or (math-objectp rate) (and math-expand-formulas (null lump))
      (math-reject-arg rate 'numberp))
  (and (math-zerop rate)
       (math-reject-arg rate 'nonzerop))
  (or (math-objectp pmt) (and math-expand-formulas (null lump))
      (math-reject-arg pmt 'numberp))
  (or (math-objectp amount) (and math-expand-formulas (null lump))
      (math-reject-arg amount 'numberp))
  (if lump
      (progn
	(or (math-objectp lump)
	    (math-reject-arg lump 'numberp))
	(let ((root (math-find-root (list 'calcFunc-eq
					  (list (if bflag
						    'calcFunc-pvb
						  'calcFunc-pv)
						rate
						'(var DUMMY var-DUMMY)
						pmt
						lump)
					  amount)
				    '(var DUMMY var-DUMMY)
				    '(intv 3 0 100)
				    t)))
	  (if (math-vectorp root)
	      (nth 1 root)
	    root)))
    (math-with-extra-prec 2
      (let ((temp (if (eq bflag 'l)
		      (math-div amount pmt)
		    (math-sub 1 (math-div (math-mul amount rate)
					  (if bflag
					      (math-mul pmt (math-add 1 rate))
					    pmt))))))
	(if (or (math-posp temp) math-expand-formulas)
	    (math-neg (calcFunc-log temp (math-add 1 rate)))
	  (math-reject-arg pmt "*Payment too small to cover interest rate"))))))