Re: Instantiating package problems

[Andrew Shvets <andrew.shvets@gmail.com>]

Hi Bob,

Thanks for writing back.  This is the entire example:
http://pastebin.com/GEJT3WzL

Thanks for the tip on compiling.

On Sunday, January 3, 2016 at 5:08:53 PM UTC-5, Bob Duff wrote:
> Andrew Shvets <andre.....@gmail.com> writes:
> 
> > This is coming from the perspective of someone that has far more C++ OOP
> > experience.
> 
> Ada has "packages" and "types".  C++ combines these into one feature
> (the "class").  I suspect that difference explains your confusion.
> 
> >...Basically, what I'm trying to do is create an instance of a
> > package and then call a function from that object.
> 
> There's no such thing as an instance of a package in Ada.
> An instance of a generic package (which is sort of like a C++ template)
> is a package, not an object.  An instance of a type is
> an object.
> 
> >...This is what I have below.
> > The calculator package is a simple package with the Addition function (which,
> > you guessed it, just adds numbers together) that takes two integers and returns
> > an integer.
> >
> > I think I'm not quite getting this right or I've misunderstood something.  Here
> > is my code so far and the results that I get when I compile it.
> >
> > =========================================================
> > with Ada.Text_IO;
> >
> > with Calculator;
> >
> > procedure Main is
> >   Calc : Calculator;
> 
> Better to show a complete example.
> 
> But anyway, Calculator is a package, not a type.
> I think you can get rid of this line.
> I'm guessing there are no types declared in Calculator.
> 
> > begin
> >   ...
> >
> >   Ada.Text_IO.Put_Line(" Addition:       " & Integer'Image(Calc.Addition(52, 31)));
> 
> I think you can just call Calculator.Addition.  I can't be sure without
> a complete example.
> 
> By the way, I don't see anything object-oriented in this example.
> It looks like you're just trying to call a function that is declared
> in a package -- no need to create any objects here.
> 
> >   Ada.Text_IO.New_Line;
> > end Main;
> >
> > OUTPUT:$ gnatmake -g main.adb calculator.adb
> 
> You don't need to tell gnatmake all the files.  Just the main
> procedure -- it can find all the other files that need to be
> [re]compiled based on the "with"s (etc.).
> 
> - Bob