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Date: Fri, 27 Nov 2015 07:25:57 -0800 (PST)
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Subject: Two approaches of iterators for the key-value pairs
From: ytomino <aghia05@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:28559
Date: 2015-11-27T07:25:57-08:00
List-Id: <comp.lang.ada>

Hello, I'm reading AI12-0009-1 "Iterators for Directories and Environment_Variables".
http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai12s/ai12-0009-1.txt?rev=1.4

And there is interesting difference between the new iterator of Ada.Environment_Variables and the existing iterators.
(The boolean trick of these new iterators is also interesting, but set aside.)

A loop for Ada.Environment_Variables would be like below, according to this AI:

for E *of* Ada.Environment_Variables.All_Variables loop
   -- E is Iterator_Element (Name_Value_Pair_Type)
   Name (E) -- key
   Value (E) -- value
end loop;

On the other hand, as we already know, a loop for Ada.Containers.Hashed_Maps/Ordered_Maps:

for I *in* The_Map_Object.Iterate loop
   -- I is Cursor
   Key (E) -- key
   Element (E), Reference (E).Element.all -- value
end loop;

If you create new iterator for some key-value pairs, which approach do you like?

-- 
Yuta Tomino