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Re: Why is booleanp defined this way?
From: |
Rusi |
Subject: |
Re: Why is booleanp defined this way? |
Date: |
Fri, 17 Apr 2015 19:01:11 -0700 (PDT) |
User-agent: |
G2/1.0 |
On Saturday, April 18, 2015 at 2:05:11 AM UTC+5:30, Marcin Borkowski wrote:
> Hi all,
>
> this is what I found in subr.el:
>
> ,----
> | (defun booleanp (object)
> | "Return t if OBJECT is one of the two canonical boolean values: t or nil.
> | Otherwise, return nil."
> | (and (memq object '(nil t)) t))
> `----
>
> Seemingly, it doesn't make much sense: what is the purpose of saying
>
> (and (whatever) t)
>
> instead of just
>
> (whatever)
>
> for a predicate? Of course, this "normalizes" any "truthy" value to
> "t", but is it really needed for anything (except perhaps being
> elegant)?
>
> Best,
Elisp does not have a proper boolean type; unlike say symbols with
symbolp, strings with stringp, numberp -- some union of numeric types etc.
However programmers need boolean in their ontology even if (and even more if)
the language does not support it.
I'd say booleanp is a hesitant step towards supporting boolean in the ontology
without supporting it in the language.
- Re: Why is booleanp defined this way?, (continued)
RE: Why is booleanp defined this way?, Drew Adams, 2015/04/17
Re: Why is booleanp defined this way?, Tassilo Horn, 2015/04/18
Re: Why is booleanp defined this way?, Pascal J. Bourguignon, 2015/04/17
Re: Why is booleanp defined this way?, Barry Margolin, 2015/04/17
Re: Why is booleanp defined this way?,
Rusi <=
- Re: Why is booleanp defined this way?, Emanuel Berg, 2015/04/17
- Re: Why is booleanp defined this way?, Rusi, 2015/04/17
- Re: Why is booleanp defined this way?, Emanuel Berg, 2015/04/17
- Re: Why is booleanp defined this way?, Barry Margolin, 2015/04/17
- Re: Why is booleanp defined this way?, Rusi, 2015/04/17
- Re: Why is booleanp defined this way?, Barry Margolin, 2015/04/18
- Re: Why is booleanp defined this way?, Emanuel Berg, 2015/04/19
- Re: Why is booleanp defined this way?, Emanuel Berg, 2015/04/19
Re: Why is booleanp defined this way?, Emanuel Berg, 2015/04/18
Re: Why is booleanp defined this way?, Marcin Borkowski, 2015/04/18