On Thu, 20 Jun 2013, Ralph Boland wrote:

> I am using Squeak  3.11.  I assume the same results apply to Squeak 4.4.  If not, my apologies.

LargePositiveInteger >> #bitAnd: is not present in Squeak 4.4.

> 
> In Squeak if I evaluate:
> 
> 1)  ((2 << 256)  bitAnd: (2 << 128)) ==>  0
> 2)  ((2 << 256)  bitAnd: (2 << 128)) class ==> SmallInteger
> 3)  (2 << 128)                               ==>  680564733841876926926749214863536422912
> 4)  ((2 << 128) bitAnd: (2 << 128))  ==>  680564733841876926926749214863536422912
> 
> This all looks correct and I care because I need to do <bitAnd:> of some largePositiveIntegers.
> 
> But <LargePositiveInteger>>BitAnd:>  is:
> 
> "Primitive. Answer an Integer whose bits are the logical AND of the
>     receiver's bits and those of the argument. Fail if the receiver or argument
>     is greater than 32 bits. See Object documentation whatIsAPrimitive."
>     <primitive: 14>
>     self halt.          "I ADDED THE HALT"
>     ^ super bitAnd: anInteger
> 
> The way I see it  <LargePositiveInteger>>BitAnd:>   is always going to fail and thus invoke its super version
> (<LargePositiveInteger>>BitAnd:>)  and this is what I see when I run the code; i.e. I hit the halt.
> 
> So why have <LargePositiveInteger>>BitAnd:> method at all?

As the comment says: primitive 14 works for nonnegative SmallIntegers and 
all LargePositiveIntegers which can be represented in 4 bytes, so all 
values up to 4294967295.

In your image the following expression should use the primitive:

 	4294967295 bitAnd: 1

In this case the primitive should fail:

 	4294967296 bitAnd: 1


Levente

> 
> Ditto for the other bit operations.
> 
> Ralph Boland
> 
>