Re: Containers with Ada

[Robert Dewar <robert_dewar@my-deja.com>]

In article <8v8pii$dvo$1@nnrp1.deja.com>,
  jeltsch@my-deja.com wrote:
>    1. Copying of large data structures
>    In my opinion one main problem of Ada is implicit copying
> of variables. So
>    it's no good idea to define such a intuitive function like
>       function Element_At(Current_List : in List;
Current_Index : in Index)
>                          return Element;
>    In this example the list which could contain thousands of
elements would
>    be copied just to get one element out of it.


This is such a fundamental misconception, that you need to
go back and start at square one. No compiler I can imagine
would decide that it was more efficient to copy this list
if it had thousands of elements.

You seem to have somehow picked up the idea that IN parameters
are always copied. This of course is NOT the case in Ada.
Indeed the expectation is precisely that large objects passed
as IN parameters will be passed by reference. The compiler makes
the choice based on what is most efficient. YOU are NOT in the
business of worrying about efficiency at this level, and as
you show, if you do start worrying, you are very likely to get
yourself seriously confused :-)


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