Recent versions of Emacs support lexical binding for variables in elisp code. Is it also possible to lexically redefine functions? In other words, does Emacs Lisp have something like lexical-flet?
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Ryan C. Thompson
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In Emacs<24.3, you can (require 'cl) and then use labels. In Emacs-24.3 and up, you can also do (require 'cl-lib) and then use either cl-flet or cl-labels.
All of those are "complex macros" that generate code that looks like (let ((fun (lambda (args) (body)))) ... (funcall fun my-args) ...), because the underlying language does not natively support local function definitions.
Stefan
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I'm switching to this as the accepted answer, since it is more complete and gives the full background. – Ryan C. Thompson Dec 13 '12 at 01:37
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There is labels but I don't know if that's what you're looking for:
(defun foo ()
42)
(defun bar ()
(foo))
(list
(foo)
(bar)
(labels ((foo ()
12))
(list (foo)
(bar)))
(foo)
(bar))
It returns (42 42 (12 42) 42 42).
Ryan C. Thompson
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Daimrod
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To me 24.2.1 returns "Symbol's function definition is void: labels" – Miserable Variable Dec 12 '12 at 23:13
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`(require 'cl)`. If you have a recent enough version, use `(cl-labels ...)` instead. – Hugh Dec 13 '12 at 00:12
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The docstring says "This is like `flet`, except the bindings are lexical". That's exactly what I wanted. Thanks! – Ryan C. Thompson Dec 13 '12 at 01:17