Tail call optimization for Emacs.

recur means recursive call (like clojure). All recur must be called on tail.

(recur-loop                             ;Same as `recur-let'
    ((x 5)
     (y 1))
  (if (eq x 0)
      y
    (recur (1- x) (* x y))))
;; => 120

(recur-progv '(x y) '(5 1)
  (if (eq x 0)
      y
    (recur (1- x) (* x y))))
;; => 120

(recur-defun factorial (x &optional y)
  (setq y (or y 1))
  (if (eq x 0)
      y
    (recur (1- x) (* x y))))
;; => factorial

(factorial 5 1)
;; => 120

(factorial 5)
;; => 120

(recur-defun sum (init &rest list)
  (if list
      (recur (+ init (car list))
             (cdr list))
    init))
;; => sum

(sum 1 2 3 4 5)
;; 15

How to Use?

recur-loop / recur-let

Recursively callable let. Similar to loop in clojure. This is same as recur-progv, except using BINDINGS like let instead of SYMBOLS and INITVALUES. BODY is evaluated with variables set by BINDINGS.

Note that recur MUST be tail recursion and this macro optimize tail call.

recur-progv

Recursively callable cl-progv. SYMBOLS, INITVALUES (as VALUES), and BODY are same as arguments of cl-progv. In addition, you can use function recur in BODY form. This function take arguments same number as length of SYMBOLS, and evaluate BODY form with SYMBOLS bounded by each value of arguments.

Note that recur MUST be tail recursion and this macro optimize tail call.

recur-defun

Define function with tail call optimization. NAME, ARGLIST, DOCSTRING and BODY is same as arguments of defun. recur in BODY calls the function named NAME itself with arguments. recur cannot recieve variable length arguments, so you must pass one list even as &rest argument.

Note that recur MUST be tail recursion and this macro optimize tail call.

License

This package is licensed by GPLv3. See LICENSE.