Strings

[Jef Kelmo <jlk@vdu.org>]

Hello,

    This is not a homework question. In 5 months, I will begin work that
uses Ada and am trying to become familiar with it now. But I am having a
problem with how to use strings; a problem that seems common across a
number of languages, including C++ and Java.

    I entered the following...

----------------------------------------------------------------------------------------------------------

with Ada.Text_IO;
with Ada.Strings.Bounded;

procedure My_Strings is
    type Bounded_80 is new
Ada.Strings.Bounded.Generic_Bounded_Length(80);

    a1 : Bounded_80.Bounded_String := Bounded_80.To_Bounded_String("Some
Text");

begin
    Ada.Text_IO.Put(Bounded_80.To_String(a1));
    Ada.Text_IO.New_Line;

end My_Strings;
----------------------------------------------------------------------------------------------------------

 ...and when I compile, I get the following...

gcc -c my_strings.adb
my_strings.adb:5:47: subtype mark required in this context
my_strings.adb:5:70: incorrect constraint for this kind of type
my_strings.adb:7:10: invalid prefix in selected component "Bounded_80"
my_strings.adb:7:39: invalid prefix in selected component "Bounded_80"
my_strings.adb:12:21: invalid prefix in selected component "Bounded_80"
gnatmake: "my_strings.adb" compilation error


    So my first guess is to change...

    type Bounded_80 is new
Ada.Strings.Bounded.Generic_Bounded_Length(80);

    ...to...

    subtype Bounded_80 is new
Ada.Strings.Bounded.Generic_Bounded_Length(80);

    ...in which case I get...

gcc -c my_strings.adb
my_strings.adb:5:27: "new" ignored (only allowed in type declaration)
gnatmake: "my_strings.adb" compilation error

    ...so I remove the "new" and get...

gcc -c my_strings.adb
my_strings.adb:5:46: subtype mark required in this context
my_strings.adb:5:69: incorrect constraint for this kind of type
my_strings.adb:7:10: invalid prefix in selected component "Bounded_80"
my_strings.adb:7:39: invalid prefix in selected component "Bounded_80"
my_strings.adb:12:21: invalid prefix in selected component "Bounded_80"
gnatmake: "my_strings.adb" compilation error

    Is it obvious by now that I don't know what I am doing? I have a
copy of Ada as a 2d Language and I looked up the Ada Reference on
adapower.com, but everything is too vague and anything I try does not
work.

    I just want a usable string. How would I change the above code to do
this? And could someone please point me to a site that gives actual,
concrete examples of simple string use?

    Thanks.

James