multiplication bug in director 9999*999999

[YM]

I am programming catalog of prodacts- some of them cost 9999.99 so in my
field i
put 7 chars option for the price.
I put 4 chars for units number so- when some one will do 9999*999999 the
resolt is in correct (someTimes it is minus!!!)
try to do this in the msg "put 999999*9999" and you will see what i am
talking about.
if some budy knows the answer to this bug please contact me in
u...@poenta.co.il
thanks udi.

[Andrew Morton]

(I needed a couple more 9's to get the error.)
Not a bug so much as a failure to trap overflow when multiplying signed 32-bit integers.
Try put the maxInteger +1 for a similar result.
If you put 99999.0*9999999 it gives the correct result as you've forced it to use
floating-point numbers.

Andrew Morton

[Vince Brokop]

i'm using director 8... this is really odd! i can get up to 99999*9999 and
still get the correct answer... add one more 9, and while i do get a
positive number, it is incorrect according to my handy calculator here, AND
windows calculator.
i don't know what to tell you... you're going to have to find a workaround
of some sort.

[Luke Wigley]

in article 3A0A19BC...@fulltiltmedia.com, Vince Brokop at
vbr...@fulltiltmedia.com wrote on 9/11/00 2:27 PM:

> i'm using director 8... this is really odd! i can get up to 99999*9999 and
> still get the correct answer... add one more 9, and while i do get a
> positive number, it is incorrect according to my handy calculator here, AND
> windows calculator.
> i don't know what to tell you... you're going to have to find a workaround
> of some sort.

There is a maximum integer that is supported by the system. In lingo, you
can test what the biggest integer is with the 'maxInteger' system property.
Eg.

-- Welcome to Director --
put the maxInteger
-- 2147483647

In 32-bit systems, this number is 2 to the power of 31 minus 1 (its 2 to the
power of 31, not 32, because the extra bit is used to sign the integer as
either positive or negative).

Signed-32bit integers are represented with four bytes. This makes them very
quick to process. If you are working with big numbers, then use floats which
can be bigger than 4 bytes (though processing floating numbers is inherently
slower than processing integers).

Incidently, if you type this into the message window

put power(2, 31)-1
-- 2147483647.0000

You will notice that the power function seems to automatically type-change
integers into floats, probably because the risk of creating big numbers.
However, if you multiply two integers -- then Director will try and keep
them as integers, even if the result is too big.

Luke
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