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Re: with a fresh emacs "(buffer-local-value fundamental-mode (current-b


From: Davis Herring
Subject: Re: with a fresh emacs "(buffer-local-value fundamental-mode (current-buffer))" error.
Date: Thu, 16 Apr 2009 14:29:02 -0700 (PDT)
User-agent: SquirrelMail/1.4.8-5.3.lanl2

>> This should be (bound-and-true-p longlines-mode), because the
>> bound-and-true-p macro treats its VAR argument like setq; it is a macro,
>> not an ordinary Lisp function.  Its docstring needs to be
>> corrected---I'll do this once I when I get the chance.
>
> It's too bad: it should have been a function, but it's a bit late to fix
> it now.

My apologies for, in a message meant to educate about the vagaries of
quoting, not noticing that it was a macro.  On the subject of having it be
a function, it wouldn't be too horrible to provide a function also: I
would suggest the name `symbol-value-safe' (in line with `car-safe').  I
have this function defined as

(defun symbol-value-safe (symbol &optional def)
  "Return SYMBOL's value, or DEF if that is void."
  (if (boundp symbol) (symbol-value symbol) def))

One use of the default is for cross-version compatibility:

(symbol-value-safe 'eval-expression-print-length 12) ; for Emacs 20

Davis

-- 
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