Numerics, NaNs, IEEE 754 and C99

[Grant Edwards]

On 2006-06-15, Tim Peters <tim.peters at gmail.com> wrote:

> [Grant]
>> Am I remebering incorrectly?
>
> Mostly but not entirely.
>
>> Didn't the old fixed-width integers operate modulo-wordsize?
>
> Not in Python.
>
>> I distinctly remember having to rewrite a bunch of checksum code when
>> fixed-width integers went away.
>
> Best guess is that you're working on a 32-bit box, and remember this
> Python <= 2.2 behavior specific to the left shift operator:
>
>>>> 1 << 31
> -2147483648
>>>> 1 << 32
> 0

That's probably it.

I've also spent some time on/off fighting with 32-bit constants
that have the high-order bit set.  You've got to jump through
hoops when you need to pass a value like 0xC0000000 to an
extension that demands a 32-bit value.

> + - * / on short ints always complained about overflow before
> int-long unification,

I was definitely mis-remembering things.  I had to have been
the left shift that caused the problems.

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