Function: byte-optimize-cond

byte-optimize-cond is a byte-compiled function defined in byte-opt.el.gz.

Signature

(byte-optimize-cond FORM)

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/byte-opt.el.gz
(defun byte-optimize-cond (form)
  ;; if any clauses have a literal nil as their test, throw them away.
  ;; if any clause has a literal non-nil constant as its test, throw
  ;; away all following clauses.
  (let (rest)
    ;; This must be first, to reduce (cond (t ...) (nil)) to (progn t ...)
    (while (setq rest (assq nil (cdr form)))
      (setq form (remq rest form)))
    (setq form (remq nil form))
    (setq rest form)
    (while (setq rest (cdr rest))
      (cond ((byte-compile-trueconstp (car-safe (car rest)))
             ;; This branch will always be taken: kill the subsequent ones.
	     (cond ((eq rest (cdr form)) ;First branch of `cond'.
		    (setq form `(progn ,@(car rest))))
		   ((cdr rest)
		    (setq form (copy-sequence form))
		    (setcdr (memq (car rest) form) nil)))
	     (setq rest nil))
            ((and (consp (car rest))
                  (byte-compile-nilconstp (caar rest)))
             ;; This branch will never be taken: kill its body.
             (setcdr (car rest) nil)))))
  ;;
  ;; Turn (cond (( <x> )) ... ) into (or <x> (cond ... ))
  (if (eq 'cond (car-safe form))
      (let ((clauses (cdr form)))
	(if (and (consp (car clauses))
		 (null (cdr (car clauses))))
	    (list 'or (car (car clauses))
		  (byte-optimize-cond
		   (cons (car form) (cdr (cdr form)))))
	  (and clauses form)))
    form))