Subtracting Large Numbers

[Bruce]

I am puzzled by the following code:

<?php
print "<p>MaxInt=".PH P_INT_MAX;
$AA = -190668411;
$BB = -2181087916;
print "<br>AA=$AA ";
print "<br>BB=$BB ";
$AA = (int)$AA + (int)$BB;
print "<br>AA+BB=$AA" ;
?>

On some systems, I get:

MaxInt=21474836 47
AA=-190668411
BB=-2181087916
AA+BB=-2338152059

On others, I get:

MaxInt=21474836 47
AA=-190668411
BB=-2181087916
AA+BB=192321096 9

Why the difference?

Thanks...Bruce

[Michael Austin]

Re: Subtracting Large Numbers

Bruce wrote:[color=blue]
> I am puzzled by the following code:
>
> <?php
> print "<p>MaxInt=".PH P_INT_MAX;
> $AA = -190668411;
> $BB = -2181087916;
> print "<br>AA=$AA ";
> print "<br>BB=$BB ";
> $AA = (int)$AA + (int)$BB;
> print "<br>AA+BB=$AA" ;
> ?>
>
> On some systems, I get:
>
> MaxInt=21474836 47
> AA=-190668411
> BB=-2181087916
> AA+BB=-2338152059
>
> On others, I get:
>
> MaxInt=21474836 47
> AA=-190668411
> BB=-2181087916
> AA+BB=192321096 9
>
> Why the difference?
>
> Thanks...Bruce[/color]

http://us2.php.net/intval

"The maximum value depends on the system. 32 bit systems have a maximum signed
integer range of -2147483648 to 2147483647. So for example on such a system,
intval('1000000 000000') will return 2147483647. The maximum signed integer value
for 64 bit systems is 922337203685477 5807."

Depends on system, OS, math libraries, cpu type etc...

--
Michael Austin.
Consultant - Available.
Donations welcomed. Http://www.firstdbasource.com/donations.html
:)

[Bruce]

Re: Subtracting Large Numbers

Actually, this appears to be an issue with how floats are converted to
ints. For example:

$BB = -2181087916;
$AA = (int)$BB;
$AA = intval($BB);

On some systems, $AA will be int(-2147483648), which is actually
consistent with the documentation.

On most systems, however, $AA will be int(2113879380) , which is the
same value truncated at 32 bits.

I actually need the latter behavior, as it needs to duplicate Delphi
code, which, like C, behaves the same way.

Any ideas how I can do this?


On Fri, 17 Feb 2006 23:43:49 GMT, Michael Austin
<maustin@firstd basource.com> wrote:
[color=blue]
>
>"The maximum value depends on the system. 32 bit systems have a maximum signed
>integer range of -2147483648 to 2147483647. So for example on such a system,
>intval('100000 0000000') will return 2147483647. The maximum signed integer value
>for 64 bit systems is 922337203685477 5807."
>
>Depends on system, OS, math libraries, cpu type etc...[/color]