Juliant at 22:32, 3 July 2007

2007-07-03T22:32:55Z

Peter gummer at 08:54, 3 July 2007

2007-07-03T08:54:48Z

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--[[User:Peter gummer|Peter gummer]] 10:54, 3 July 2007 (CEST) It is annoying that, in order to solve the catcall problem, we have to forbid polymorphic assignments like <e>list_of_any := list_of_string</e>. Yes, we don't want integers poked into <e>list_of_any</e> when it's attached to a list of strings; but usually when we perform such assignments it's so that we can use the list in a read-only fashion. I would prefer to allow such assignments, if and only if the entity on the left is declared '''read-only'''. ''Uh oh'', now I've gone and raised the old question, "C++ has ''const'' so why doesn't Eiffel?"

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	--[[User:Peter gummer\|Peter gummer]] 10:54, 3 July 2007 (CEST) It is annoying that, in order to solve the catcall problem, we have to forbid polymorphic assignments like <e>list_of_any := list_of_string</e>. Yes, we don't want integers poked into <e>list_of_any</e> when it's attached to a list of strings; but usually when we perform such assignments it's so that we can use the list in a read-only fashion. I would prefer to allow such assignments, if and only if the entity on the left is declared '''read-only'''. ''Uh oh'', now I've gone and raised the old question, "C++ has ''const'' so why doesn't Eiffel?"		--[[User:Peter gummer\|Peter gummer]] 10:54, 3 July 2007 (CEST) It is annoying that, in order to solve the catcall problem, we have to forbid polymorphic assignments like <e>list_of_any := list_of_string</e>. Yes, we don't want integers poked into <e>list_of_any</e> when it's attached to a list of strings; but usually when we perform such assignments it's so that we can use the list in a read-only fashion. I would prefer to allow such assignments, if and only if the entity on the left is declared '''read-only'''. ''Uh oh'', now I've gone and raised the old question, "C++ has ''const'' so why doesn't Eiffel?"
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		+	'''--[[User:Juliant\|Juliant]] 00:32, 4 July 2007 (CEST)''':
		+	The assignment has to be disallowed with ''default semantics''. A good solution will allow exactly what you say, an easy way to declare a read-only list. For example the [[usage-site variance]] would allow to declare a list as <e>LIST [+ANY]</e> to mark it read-only.
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		+	The last ECMA meeting proposed a new solution but we didn't get the validity rules yet, so we don't have a wiki-page for this at the moment. We will add this when we get them and then we can see how it works there.

Talk:Catcall checkpoints - Revision history

Juliant at 22:32, 3 July 2007

Peter gummer at 08:54, 3 July 2007