Re: [Newbies] Testing = and == in workspace
On 08.01.2012, at 00:48, Ben Coman wrote:
For some naive reason I thought that the SmallIntegers would stop at 64k.
No, SmallIntegers currently use the full 31 bit range:
{SmallInteger maxVal hex. SmallInteger minVal hex}
== #('16r3FFF' '-16r4000')
Is it platform dependent on whether the CPU is 16/32/64 bit ?
Squeak is independent of the CPU word size. All images in general use are 32
bits. That means an object pointer (aka oop) is a 32 bit word. Squeak's
ancestor, Smalltalk-80, used 16 bit oops. For Squeak there is an experimental
64 bit image format, where each object pointer uses 64 bits. (1)
Normally an oop references a chunk of memory, which has one to three header
words, and zero or more words for the contents of the object.
Only SmallIntegers are special: their oops do not reference memory, but the
value is taken from the bits of the oop itself. Each oop has one tag bit
which determines if it is a normal oop (a reference) or an immediate object.
The other 31 bits determine the value of the SmallInteger. (2)
That's why two SmallIntegers with the same value are always identical. ==
simply compares oops.
- Bert -
(1) 64 bit VM means a VM compiled for a 64 bit processor, 64 bit image
means an image that use 64 bit oops. These are independent concepts, a 64 bit
VM may run a 32 bit image. See http://squeakvm.org/squeak64/faq.html
(2) There have been proposals to use more tag bits, which would reduce the
range of SmallIntegers, but add more immediate classes. There have been
experiments but nothing has been officially adopted yet. But in particular with
64 bit oops there are so many bits that we may see more immediate classes.
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Re: [Newbies] Testing = and == in workspace
Am 07.01.2012 um 07:04 schrieb Ben Coman b...@openinworld.com: I had thought that the two assignments of 'xxx' to (x) and (y) would result in different objects, but they turn out to be identical. It is like the compiler has noticed that they are equal and chosen to make them identical. That is indeed what's happening. You can verify this by executing each line separately. - Bert -___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Testing = and == in workspace
Bert Freudenberg wrote: Am 07.01.2012 um 07:04 schrieb Ben Coman b...@openinworld.com: I had thought that the two assignments of 'xxx' to (x) and (y) would result in different objects, but they turn out to be identical. It is like the compiler has noticed that they are equal and chosen to make them identical. That is indeed what's happening. You can verify this by executing each line separately. Thanks Bert. Doing that is insightful. Interestingly the result is different with numbers. Where strings assigned in separate executions are not identical, numbers assigned in separate executions are identical - at lower values. For example, number 12345678 has (x) and (y) identical but with 123456789 they are not. I then expected those number literals to be a different class, but both numbers inspect as SmallIntegers. btw this is with Pharo-1.3-13315-cog2522. Anyway, my curiosity is satisfied for now. cheers, Ben ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Testing = and == in workspace
Levente Uzonyi wrote: On Sat, 7 Jan 2012, Ben Coman wrote: Bert Freudenberg wrote: Am 07.01.2012 um 07:04 schrieb Ben Coman b...@openinworld.com: I had thought that the two assignments of 'xxx' to (x) and (y) would result in different objects, but they turn out to be identical. It is like the compiler has noticed that they are equal and chosen to make them identical. That is indeed what's happening. You can verify this by executing each line separately. Thanks Bert. Doing that is insightful. Interestingly the result is different with numbers. Where strings assigned in separate executions are not identical, numbers assigned in separate executions are identical - at lower values. For example, number 12345678 has (x) and (y) identical but with 123456789 they are not. I then expected those number literals to be a different class, but both numbers inspect as SmallIntegers. btw this is with That's impossible, SmallIntegers with the same value are identical. Levente Pharo-1.3-13315-cog2522. Anyway, my curiosity is satisfied for now. cheers, Ben I could have sworn I observed that behaviour last night, with the difference between the 8th and 9th digit, being SmallIntegers in both cases, but this morning I can't replicate it. Now the difference is between the 9th and 10th digits, which makes more sense they become LargePositiveIntegers with the 10th digit. I put it down to fatigue from being up too late. (though I would have sworn...) As a final thing. For some naive reason I thought that the SmallIntegers would stop at 64k. Is it platform dependent on whether the CPU is 16/32/64 bit ? ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
RE: [Newbies] Testing = and == in workspace
Hi Ben, Have a look at the method for yourself. Check out the method = on the instance side of String. It should be pretty obvious when you get to the actual string comparison. All the best, Ron Teitelbaum -Original Message- From: beginners-boun...@lists.squeakfoundation.org [mailto:beginners- boun...@lists.squeakfoundation.org] On Behalf Of Ben Coman Sent: Saturday, January 07, 2012 12:15 AM To: A friendly place to get answers to even the most basic questions about Squeak. Subject: [Newbies] Testing = and == in workspace I was trying to confirm the operation of = and == in the workspace by executing the following code.. x := 'xxx'. y := 'xxx'. z := x. (OrderedCollection new) add: (x = y) ; add: (x == y) ; add: (x=z); add: (x==z); yourself. I was confused that I was getting anOrderedCollection(true true true true) It was not until I changed to the following code... x := String newFrom: 'xxx'. y := String newFrom: 'xxx'. z := x. (OrderedCollection new) add: (x = y) ; add: (x == y) ; add: (x=z); add: (x==z); yourself. that I got the expected anOrderedCollection(true false true true) I was curious what was going on in the first case. cheers, Ben ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
