ichimal / local-function

local-function: a variant of named-let with no-return feature

LOCAL-FUNCTION

A variant of named-let of Scheme language, which supports following special features;

• NO-RETURN
• GLOBAL-EXIT-FROM-LOCAL-FUNCTION

description:

LOCAL-FUNCTION enables to describe and execute recuresive local function which is similar to the named-let in Scheme language.

LOCAL-FUNCTION supports NO-RETURN function call feature, which will be translated into a GO expression. NO-RETUREN can be located anywhere upon local-function body.

NOTE: just on this implementation, NO-RETURN not supported to call other functions.

NOTE: TCO for non NO-RETURN style recursive call is not guaranteed.

LOCAL-FUNCTION also supports GLOBAL-EXIT-FROM-LOCAL-FUNCTION, similar to RETURN, for global exit from a local function.

example:

(defun fx (x)
  (declare (integer x))
  (local-function f ((i x)) (sum 0)
    (declare (integer i sum))
    (when (> i 0)
      (no-return (f (the integer (1- i)) (the integer (+ sum i)))) )
    (format t \"~&SUM is ~a~%\" sum)
    (global-exit-from-local-function sum) ))  ; or, just sum

will be expanded to

(defun fx (x)
  (declare (integer x))
  (block #1=#:G1
    (labels
      ((f (#3=#:G3 #4=#:G4)
         (declare (integer #3# #4#))
         (tagbody #2=#:G2
           (let ((i #3#) (sum #4#))
             (declare (integer i sum))
             (return-from f
               (progn
                 (if (> i 0)
                   (progn
                     (psetq i (the integer (1- i))
                            sum (the integer (+ sum i)))
                     (go #2#) ))
                 (format t \"~&SUM is ~a~%\" sum)
                 (return-from #1# sum) ))))))    ; or, just sum
      (f x 0) )))

and enable to execute pseudo recursive call deeper than deeper.

> (fx 100000000)
SUM is 5000000050000000
5000000050000000
>

License:

Under MIT license.