A simple alternative to Scheme's LETREC.

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Robert Smith <quad@symbo1ics.com>


Public Domain. See LICENSE.
LETREC ====== Robert Smith INTRODUCTION ------------ LETREC:LETREC is a macro which aims to imitate Scheme's letrec form. It is a useful construct for functional programming in Common Lisp, where you have function-producing forms which need to be functionally bound to a symbol. EXAMPLE ------- The following code (defun multiplier (n) (lambda (x) (* n x))) (letrec ((double (multiplier 2)) (triple (multiplier 3))) (double (triple 5))) produces 30. Another example: (letrec:letrec ((double (multiplier 2))) (double (funcall #'double 5))) produces 20. ISSUES ------ Unforunately, the macro isn't a very efficient implementation. There is a level of indirection with the function calling. Essentially, a LETREC with the binding (name fn) is expanded to a LABELS binding of the form (name (&rest args) (apply fn args)) which is somewhat abysmal. Patches are welcome for implementation-specific ways of implementing the macro.

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  • alexandria

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    • GitHub
    • Quicklisp