Re: pi seems not to be a constant

On Tue, Oct 20, 2015 at 12:28 AM, Don Cohen
<[email protected]> wrote:
> Pierpaolo Bernardi writes:
>  > A typical use case for adjustable precision floats is the following:
>  >
>  > (setf (ext:long-float-digits) some-appropriate-number-of-bits)
>  > (large-body-of-standard-portable-cl-code-using-long-floats)
>  >
>  > If long-float-digits is changed and the "constants" are not adjusted
>  > then STANDARD PORTABLE CL code will break.
>
> I don't understand what you think will go wrong.
> Please specify.

Portable, standard, CL code expects the value of
MOST-POSITIVE-LONG-FLOAT to be the most positive long float value.

With your proposal, the example case I described above won't work.
Since I think the above case is an important one, I wouldn't be happy
if Clisp changed in this way.

OK, portable, standard, CL code expects also MOST-POSITIVE-LONG-FLOAT
to be a constant, but, for some reason, this does not worry me.

>  > And if you use it then everything breaks.  So removing it will
>  > avoid troubles.
> I don't accept that everything breaks if you use it.  However if
> you remove it and still use it then clearly it does break.
> Given that nothing goes wrong if you DON'T use it, and you're
> guaranteeing to break code that DOES use it, removing it can only
> make things worse.

OK, I agree.  In fact I think that, if one wants to retain adjustable
precision long floats, then any change to the status quo will make
things worse.

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