On Wed, 7 Aug 2013, psea wrote:

> Ok, i've got it. So in ST it's just not allowed assign to a block argument
> for some reason. Let's consider it a language feature. And it's ok,

It's a compiler bug. The compiler doesn't handle this case.
- TempVariableNode >> #analyseClosure: returns if the receiver is a block
argument without checking the preference.
- BlockNode >> #postNumberingProcessTempsWithin:rootNode: only checks the 
temporaries, but not the arguments of the receiver.
- Even if the above two are fixed, the temp index is still out of bounds, 
because removing arguments is not supported (see 
#removeTempNode:ifAbsent: and its sender), so the original temp for the 
argument will be kept.

> different language - different rules. Thanks for pointing me on that!
> Now, I've turn off allowBlockArgumentAssignment property.
>
> What's worried me is that in other languages I'm familiar with it's a normal
> thing to assign to a function argument (Scheme, C, Python, JavaScript).

Storing into a block or method argument is considered bad practice. 
Support for it is/was planned to be removed. Even though it can yield
somewhat better performance, it's something you'll rarely see in 
Smalltalk code.

>
> answer to your questions:
> Smalltalk vmVersion 'Squeak3.10.2 of 11 February 2010 [latest update:
> #9314]'
> SmalltalkImage current systemInformationString "ditto" 'Squeak4.3
> latest update: #11860
> Current Change Set: Unnamed1'
> Windows XP.
>
> PS But you should agree with me that
>
> makeAcc := [ :acc |
>        [:n | acc:=acc+n. acc]]
>
> looks a little bit better and concise than
>
> makeAcc := [ :acc |
>        | total |
>        total:=acc.
>        [:n | total:=total+n. total]]

There's no need to explicitly return 'total' from the inner block, because 
the assignment yields the same value:

makeAcc := [ :acc |
 	| total |
 	total := acc.
 	[ :n | total := total + n ] ]


Levente

>
> :-)
>
> And thanks for the links.
>
>
>
> --
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