Defining functions Scheme-style in Common Lisp, without defun

Question

In Scheme, you define functions like

(define f (lambda (x) ...))

In particular, you can do something like this

(define f (g))

where g is some function returning a function. Is it possible to do the same in Common Lisp, i.e. to associate a function symbol with a given anonymous function?

BlenderBender · Accepted Answer · 2017-06-02 10:26:52Z

1

Nevermind, I just found the answer in Paul Graham's book ANSI Common Lisp (after looking the second time; p. 99):

(setf (symbol-function 'f) (lambda (x) (* x x)))

achieves (for most intents and purposes) the same as

(defun f (x) (* x x))

edited Jun 2, 2017 at 10:26

answered Jun 1, 2017 at 22:38

BlenderBender

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3 Comments

Sylwester Over a year ago

defun does much more than that. (macroexpand '(defun f (x) (* x x)))

BlenderBender Over a year ago

That's why I qualified the statement with "for most intents and purposes". This is mentioned in Graham's Book as well.

acelent Over a year ago

"For most intents and purposes" is quite subjective. If you're compiling files, defun informs the compiler about the function to avoid reference warnings in the same file, even if the function is declared after the references. Most implementations annotate where they found definitions such as defuns, so that an IDE or Emacs+Slime can jump to them. You don't get any of that with setf of symbol-function.

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