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RE: canonical name ending "-p"
From: |
Drew Adams |
Subject: |
RE: canonical name ending "-p" |
Date: |
Fri, 18 Mar 2011 11:31:37 -0700 |
> > Lots of things in elisp end in "-p"... is there some
> > particular meaning in this?
>
> I was told it means "predicate" long ago by the guy who
> introduced me to lisp and emacs.
Yes. It is an old Lisp idiom, not just Emacs Lisp.
> In Ruby, they use a '?' so they have 'blank?'
> -- but '?' isn't a legal character in a
> symbol so they append "p" for predicate.
This part is incorrect. `?' is perfectly legal in a Lisp symbol.
Put your cursor on a `?' char in Emacs Lisp mode and do `C-u C-x ='. You will
see this: "syntax: _ which means: symbol". Then try it:
(defun foo? () (forward-char 1))
[Unfortunately, vanilla Emacs completion treats `?' specially, so you'll need to
quote it using `C-q ?' if you want to use `C-h f' to get help on `foo?': `C-h
foo C-q ?']
> I'm curious if I have this right or not...
Yes, except for `?'.