Function: byte-optimize-letX

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

Signature

(byte-optimize-letX FORM)

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/byte-opt.el.gz
(defun byte-optimize-letX (form)
  (pcase form
    ;; Bindings list is empty.
    (`(,_ () . ,body)
     `(progn . ,body))

    ;; Body is empty or just contains a constant.
    (`(,head ,bindings . ,(or '() `(,(and const (pred macroexp-const-p)))))
     (if (eq head 'let)
         `(progn ,@(mapcar #'cadr bindings) ,const)
       `(,head ,(butlast bindings) ,(cadar (last bindings)) ,const)))

    ;; Body does nothing but return the last variable in bindings.
    (`(,head ,(and bindings
                   (let last-var (caar (last bindings))))
             ,(and last-var             ; non-linear pattern
                   (pred symbolp) (pred (not keywordp)) (pred (not booleanp))))
     (if (eq head 'let)
         `(progn ,@(mapcar #'cadr bindings))
       `(,head ,(butlast bindings) ,(cadar (last bindings)))))

    (_ form)))