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common-lisp

Named lambda in common lisp

I need to write a recursive helper function and do not need to give it global scope, but I need to reference it to achieve the recursion.

Emacs lisp has fset, which assigns to the function-cell of a symbol. What is the equivalent in common lisp?

Solution

  • I just found out that this is a idiom common enough to be in alexandria. From alexandria code:

    (defmacro named-lambda (name lambda-list &body body)
  "Expands into a lambda-expression within whose BODY NAME denotes the corresponding function."
  `(labels ((,name ,lambda-list ,@body))
 #',name))

    Here's a usage example:

    (let ((! ;; Everything can be a symbol :D
   ;; Definition here
   (named-lambda self (n)
         (case n
           (1 1)
           (otherwise (* n
                 (self (1- n)))))))) ;; Recurse here
  ;; How to call it
  (funcall ! 6))