Marco Sulla wrote:
> First, C and assembly has no boolean type.
Not to focus on this because it's not particularly relevant to the original
topic, but this isn't true: C99 added the boolean type "_Bool", which can
be aliased as "bool" with the <stdbool.h> header.
On Thu, Dec 26, 2019 at 8:53 PM Marco Sulla via Python-ideas <
python-ideas@python.org> wrote:
> Andrew Barnert wrote:
> > if you’re going to be a pedant, the floats in
> > whatever Python you’re using right now are probably 854/754-1985
> doubles, not 754-2019
> > binary64s.
>
> Mr. Andrew Barnet,
> if pedant means adhere to the standard, yes, I'm a pedant.
>
> > > This is because NaN, IMHO, it's not the right name
> > > for the entity. A number can't be Not a Number. It's an Undefined
> Number.
> > OK, so you really are arguing against IEEE float here.
>
> So now I'm no more a pedant. No, I'm an heretic, because I don't like the
> Not A Number name but I prefer Undefined Number?
> A rose with any another name has the same smell.
>
> > > But IEEE 754-2019 is written mainly for C and
> > > Assembly. And you can't return nothing in a comparison between two
> floats. So they take
> > > the most practical solution: return false.
> > > They defined a whole complicated system of signaling vs. quiet nan
> values and
> > signaling (on sNaN) vs. non-signaling operations and multiple forms of
> exception handling
> > from traps to checkable flags to substitution of default values. You can
> use much of that
> > in C (and all of it in assembly) if you want to, even if people usually
> don’t.
>
> Yes, I perfectly know, I read the specs. You forgot the payload. Thank you
> for confirming what I said.
>
> > Also, who says you can’t return nothing in a comparison between two
> floats? You can
> > write a named function that has any API you want (say, it returns -1, 0,
> 1, or NaN, or
> > even an enum of less, greater, equal, left nan, right nan, both nan,
> other incomparable)
> > instead of a Boolean function that has to return true or false.
>
> First, C and assembly has no boolean type. And I can write whatever I
> want, but IEEE 754-2019 clearly says that every comparison with NaN must
> return false, that is zero in C.
>
> > But the fact that C (and countless other languages, including Python)
> also provides the
> > operators and people use them extensively implies that many people don’t
> think the
> > operators are useless, even if you do.
>
> I never said the operators are useless. Can you quote please?
>
> > > This obviously does not apply to total ordering. Even
> > > if I think mathematically has no sense, IEEE 754 clearly defined a
> total ordering, also
> > > for NaNs. So a total_ordering() key function, passed to sort
> functions, should order as
> > > IEEE 754 declares, without raising exceptions. There's a bug opened
> somewhere about this
> > > key function.
> > > This is what I've done. Unluckily, the API now works this way. It's
> not a big problem
> > > anyway. You have only to pass as key to the sort function:
> > > def sortNans(x):
> > > try:
> > > if math.isnan(x):
> > > return float("+inf")
> > > except TypeError
> > > pass
> > >
> > > return x
> > >
> > But this isn’t the same thing that IEEE totalOrder defines.
>
> I clearly stated that the key function total_order() is being developed,
> that there's a bug opened by Tim Peters and that what I wrote has nothing
> to do with total ordering. Can you please read my post with more attention?
> It's a bit frustrating to explain the things two times, and it's not
> respectful for who writes.
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