most-positive-float, most-negative-float coming up nil

most-positive-float, most-negative-float coming up nil

[Burton Samograd]

Version: "GNU Emacs 24.0.90.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2011-10-07 on bsamograd-ubuntu"

Just playing around with emacs lisp and I thought I would try the
most-positive/most-negative variables to see numeric range. 

most-positive-fixnum
2305843009213693951
most-negative-fixnum
-2305843009213693952
most-positive-float
nil
most-negative-float
nil

Any reason why the float values are coming up nil?

--
Burton Samograd

Re: most-positive-float, most-negative-float coming up nil

[Glenn Morris]

Burton Samograd wrote:

> most-positive-float
> nil
> most-negative-float
> nil
>
> Any reason why the float values are coming up nil?

Call `cl-float-limits' first.

Re: most-positive-float, most-negative-float coming up nil

[Jambunathan K]

Burton Samograd <bsamograd@interalia.com> writes:

> Version: "GNU Emacs 24.0.90.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
>  of 2011-10-07 on bsamograd-ubuntu"
>
> Just playing around with emacs lisp and I thought I would try the
> most-positive/most-negative variables to see numeric range. 
>
> most-positive-fixnum
> 2305843009213693951
> most-negative-fixnum
> -2305843009213693952
> most-positive-float
> nil
> most-negative-float
> nil
>
> Any reason why the float values are coming up nil?

M-: (info "(cl) Implementation Parameters")

Or

M-x info-display-manual RET cl RET
i most-positive-float

will land you in a page which has the following entry.

,----
|  -- Function: cl-float-limits
|      This function makes sure that the Common Lisp floating-point
|      parameters like `most-positive-float' have been initialized.
|      Until it is called, these parameters will be `nil'.  If this
|      version of Emacs does not support floats, the parameters will
|      remain `nil'.  If the parameters have already been initialized,
|      the function returns immediately.
| 
|      The algorithm makes assumptions that will be valid for most modern
|      machines, but will fail if the machine's arithmetic is extremely
|      unusual, e.g., decimal.
`----

>
> --
> Burton Samograd
>
>
>

-- 

Re: most-positive-float, most-negative-float coming up nil

[Burton Samograd]

I did not (require 'cl) during my testing so I never thought of looking
there.  Looks like something I have loaded in my .emacs file does.  It
seems odd that most-positive/negative-fixnum are standard in emacs lisp
but not the float versions without requiring cl (plus requiring an
additional function to be called to initialize them is even more odd).
It's not like floats aren't a standard part of the emacs lisp language.

--
Burton Samograd

Re: most-positive-float, most-negative-float coming up nil

[Stefan Monnier]

> It seems odd that most-positive/negative-fixnum are standard in Emacs
> lisp but not the float versions without requiring cl (plus requiring
> an additional function to be called to initialize them is even more
> odd).  It's not like floats aren't a standard part of the Emacs
> lisp language.

Apparently nobody ever found enough of a need for most-positive-float
in Elisp (and even less so for most-negative-float).


        Stefan