Re: How to extend packages

[Stephen Leake <Stephe.Leake@nasa.gov>]

S�bastien Morand <seb.morand@gmail.com> writes:

> snoopysalive@googlemail.com a �crit :
>> Hi, Ada-folks!
>> 
>> I'd like to extend the GNAT.Regpat a little bit, so that it contains
>> additional operations like Split (the same as in Perl or Ruby) or Join
>> (dito).
>> 
>> When speaking of "extending" I mean it in the sense of e.g. Java where
>> extending a class means that the child class contains all the public
>> or protected operations and attributes as the super class. Perhaps you
>> know now, what I want to achieve. I want to have an extended "child"
>> package of GNAT.Regpat. In the end it should have an own name like
>> e.g. "Mine.Regex" and contain all operation etc. of its "super"
>> package plus the operations I'll additionally implement.
>> 
>> I've been trying for hours now, so I'm passing this question to you.
>> How to extend package?
>
> Try this:
>
> with GNAT.Regpat; use GNAT.Regpat;
>
> package GNAT.Regpat.Extended is
> end GNAT.Regpat.Extended;

This is probably the best approach.

> Then when you use GNAT.Regpat.Extended, GNAT.Regpat is available too.

This is not true. To be precise:

Suppose GNAT.Regpat declares 'foo', and GNAT.Regpat.Extended declares
'bar'.

with GNAT.Regpat.Extended;
package A is
...
end A;

Within A, you can say GNAT.Regpat.Extended.foo, or GNAT.Regpat.bar,
but 'foo' and 'bar' by themselves are not visible.

with GNAT.Regpat.Extended;
package B is
    use GNAT.Regpat.Extended;
...
end B;

Within B, you can say GNAT.Regpat.Extended.foo, or GNAT.Regpat.bar.
'foo' is visible by itself, but 'bar' is not.

with GNAT.Regpat.Extended;
package C is
    use GNAT.Regpat.Extended;
    use GNAT.Regpat;
...
end C;

Within C, 'foo' and 'bar' are both visible.

-- 
-- Stephe