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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
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Subject: Re: troubles learning OOP: expected type "Parent.Some_Child", found
 type Parent'Class
Date: Tue, 13 Feb 2018 18:42:11 +0100
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On 02/12/2018 10:18 PM, Mehdi Saada wrote:
> 
> I can't believe T_TOKEN'class is as useless... well, in a sense, since the program doesn't know the actual type of TOKEN but only that it's a child of T_TOKEN, no wonder there's some limitations. But I'm surprised there's no mechanism in the language, to tell the program: HEY there ! I'm sure it's T_TOKEN_OPERANDE, so now consider TOKEN as such and let me reach it's OPERANDE component.

Given an object V of T_Token'Class, you can do

if V in T_Token_Operateur

and

if V in T_Token_Operateur'Class

and then do a conversion to access the components of the extension. You can also 
compare V'Tag to the tags of the derived types. All of these are frowned on as 
"not the type-extension way" by aficionados of type extension.

-- 
Jeff Carter
"If you don't get the President of the United States on that
phone, ... you're going to have to answer to the Coca-Cola
Company."
Dr. Strangelove
32