[furcas-discussion] Constraints regarding ForEachContext.contextElement

[Thomas Goldschmidt]

Hi,

Maybe we should start by thinking again about the different use-cases of 
foreach and from there on define what foreach can and should do including 
a more formal view on its semantics.

I started a Wiki page for it here: 
http://www.furcas.org/wiki/index.php/Foreach-usecases

Cheers,
Thomas


 
Thomas Goldschmidt 

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"Uhl, Axel" <axel.uhl at sap.com> 
Sent by: furcas-discussion-bounces at lists.furcas.org
17.02.2011 17:49

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Subject
[furcas-discussion] Constraints regarding ForEachContext.contextElement






Hi,

looking even closer at the foreach-related code there unfortunately are 
more issues. The specification allows for foreach expressions to have a 
non-EObject result type, such as String or Boolean. I'm pretty sure this 
won't work, and we don't have test cases asserting this functionality 
which is bad. The contextElement reference in ForEachContext is typed as 
EObject. Therefore it's unable to hold String or Boolean values.

Another thing to keep in mind is that generally it is possible that a 
foreach expression results in a Bag containing several occurrences of 
equal elements for each of which an element has been produced. This in 
particular means that the corresponding ForEachContext elements have equal 
contextElement contents. What should our constraints be w.r.t. ordered 
features?

Imagine the following situation: a foreach expression may produce [e1, e2, 
e1] for which elements [f1, f2, f3] are produced. When something changes 
such that the foreach expression only produces [e1, e2] then intuitively 
speaking we may expect the feature to be updated to [f1, f2] and not [f2, 
f3}. See what I mean?

I think we should approach a more formal specification of features such as 
"foreach" because otherwise we'll end up in a big mess.

Opinions on how such a specification for the foreach-feature should look 
like?

Best,
-- Axel
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