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Re: e and pi

From: Stefan Monnier
Subject: Re: e and pi
Date: Sat, 18 Sep 2010 10:30:24 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux)

>>> This doesn't sound right---it means that people will have to make sure
>>> their function args do not coincide with any defvar, defined anywhere.
>>> It won't just be "e" and "pi" causing problems.  Someone might write
>>> (defun froob (argv)
>>> (lambda (f) (cons f argv)))
>>> and have that fail, because "argv" is a defvar defined in startup.el.
>> Exactly: hence the new warning.

> This sounds fragile.

That's been used for ages in Common-Lisp.  And it's the only reasonable
way to convert Elisp packages from dynamic-scoping to static-scoping
without having to change all `let' to something else (like lexical-let).

> If function argument names are the problem, why not just give them
> static scope, overriding any existing dynamic bindings?  While it's
> idiomatic elisp to use `let' to bind dynamic variables, AFAICT no one
> uses function arguments to do the same.

No, the issue is:

  does (let ((foo bar)) ...) bind `foo' lexically or dynamically?

-- Stefan

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