Comments on: Weird behavior of numbers in as3

By: Brandon

Brandon — Wed, 08 Sep 2010 19:10:59 +0000

Hey thanks for the article! I’m trying to get the decimal part out of a Number. I was just trying to narrow down the bits that store the decimal part so I did the following and got 0. Now I’m stuck.

trace( 1.23 & 2.23 );//0

Any suggestions?

By: Tenegri’s blog » Blog Archive » Are there real int and uint types?

Sat, 03 May 2008 15:19:40 +0000

[...] Christensen: AS3 Interesting Numeric Storage Behavior Andre Michelle: Weird behavior of numbers in as3 Michael Baczynski: Bitwise gems – fast integer math Michael Baczynski: Int, uint and number data [...]

By: bram

bram — Mon, 18 Jun 2007 08:16:41 +0000

Nikolaj, that’s pretty standard IEEE roundof errors. Have a look here:

http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems

By: Nikolaj

Nikolaj — Sun, 17 Jun 2007 20:48:27 +0000

Speaking of weird number behavior.. What is going on here?

var n:Number = 2374;
trace(n);
trace(n*.01);

Traces:

2374
23.740000000000002

By: Nate Chatellier

Nate Chatellier — Tue, 12 Jun 2007 22:26:40 +0000

Great post... but, hmm, Sho claims that his tests led him to believe that Numbers may actually be faster than ints in Flash: Grant Skinner's tests showed that ints had only a small improvement over Number, but uint was much worse then either: Michael Baczynski claims that it is converting between types is the big killer (which makes sense): It seems like the only consistent claim is that numerical data types in Flash are inconsistent ;)

By: bram

bram — Wed, 06 Jun 2007 15:17:26 +0000

Someone @ Adobe writes us back the explanation:

The AS3 VM uses 32-bit Atom formats to store various types. 3-bits of the Atom describe the type data, leaving 29-bits for actual data. In some cases, like null/undefined/void/etc, we use 3-bits plus a few more bits to define the type.

For signed integers, we have 28-bits to work with plus a sign bit. For unsigned integers we have 29-bits (or maybe 28 with the upper bit always zero?). Once your number gets larger than 28/29 bits, we dynamically switch it to a Number Atom type, which contains a 3-bit type value with a 29-bit ptr. All ptrs are 8-BYTE aligned so we get away with using 29-bits there.

All three formats are basically interchangeable. When storing a number in an Atom, we see if it’s an integer and fits within the 28/29 bits. If so, we store it as a int/uint value – otherwise we store it as a Number value.

Which, sadly enough makes total sense and is a bit of a bummer for us…

By: someone

someone — Tue, 05 Jun 2007 22:02:34 +0000

Anti-Spam: What is the sum of 7 and 3?

int