letrec

                                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.

letrec

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