Perfect!

Thanks...sorry for missing that the two were the same...

Rob

On Sun, Mar 8, 2009 at 6:47 PM, Andreas Raab <andreas.raab at gmx.de> wrote:

> That is the bug Eliot was referring to earlier. The loop variable in
> optimized to:do: loops wasn't handled correctly. Try this instead:
>
>        multiply := Array new: 4.
>        (1 to: 4) do: [:i |
>                multiply at: i put: [:x | x * i].
>        ].
>
> Note the parens around "1 to: 4" which prevents the block from being
> optimized.
>
> Cheers,
>  - Andreas
>
>
> Rob Rothwell wrote:
>
>> Ok...thanks...this is making sense!
>>
>> So...should I get the "right answer" with the new VM and the
>> 3.10.2-Closures image?
>>
>> Because...I still get 25!
>>
>> Rob
>>
>> On Sun, Mar 8, 2009 at 2:01 PM, Bert Freudenberg <bert at freudenbergs.de<mailto:
>> bert at freudenbergs.de>> wrote:
>>
>>    On 08.03.2009, at 18:13, Rob Rothwell wrote:
>>
>>        On Sun, Mar 8, 2009 at 12:38 PM, Bert Freudenberg
>>        <bert at freudenbergs.de <mailto:bert at freudenbergs.de>> wrote:
>>
>>            multiply := Array new: 4.
>>            1 to: 4 do: [:i |
>>                  multiply at: i put: [:x | x * i].
>>            ].
>>
>>            And you would rightfully assume that this is equivalent to
>>            the version above, just more concise. But now try again:
>>
>>            (multiply at: 3) value: 5.
>>
>>            The answer will, surprisingly, not be 15 in current Squeak.
>>
>>
>>        You are right!  25, in fact...
>>
>>            But with closures, the blocks would behave as expected. They
>>            are said to "close over" the state that the bound variables
>>            (i in this case) had at the time the block was created.
>>
>>
>>        So...VW does this "right," I guess, since I get 15 in VW NC 7.6?
>>
>>
>>    Yes, it has block closures.
>>
>>
>>            So basically, you can use blocks as you always have, but
>>            they will behave as you might have assumed they would.
>>
>>        So the recent VM work discussed handles this?  I will have to
>>        give that a try!
>>
>>        Thanks for the explanation!  The next question, of course, is
>>        WHY does it get 25 and not 15... ;)
>>
>>
>>
>>    Because instead of "closing over" the current value of i when the
>>    block is created, all the blocks share the same reference to i,
>>    which is actually another temporary variable of the method, instead
>>    of being local to the block. So when the block is evaluated later,
>>    the last value of i is used.
>>
>>    Now you might still expect that last value of i to be 4, but
>>    actually "1 to: 4 do:" is expanded by the compiler to a while loop
>>    like "i := 1. [i <= 4] whileTrue: [i := i + 1]", so it actually is 5
>>    after the loop terminates.
>>
>>    And all this is avoided by having real closures, the i would indeed
>>    be local to the block and not a shared temp.
>>
>>    - Bert -
>>
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>>
>
>
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