Ada Programming Language Tips

Declaring subtypes of private types

Jacob Sparre Andersen — Sat, 02 Sep 2017 16:44:00 +0300

Sometimes, you want to declare a subtype for a subset of the possible values of a private type.

You might for example want a subtype of Ada.Calendar.Time, which only can include times in the past. If Ada.Calendar.Time was a numeric type, we could declare a subset …

Building a VCS status package with Gprbuild

Jacob Sparre Andersen — Tue, 21 Feb 2017 19:30:00 +0200

Would you like your executable files to be able to tell which commit in your version control system it corresponds to?

You can do it by:

Creating a program (in this example a shell script), which generates Ada source files reporting the version control status.
Defining a "language" in Gprbuild …

Using Ada.Sequential_IO to create simple hexdump utility

Tero Koskinen — Mon, 26 Dec 2016 12:00:00 +0200

There is every now and then need for viewing the file contents as "raw" bytes shown as hex numbers. Usually, operating systems have tool 'hexdump' to do this. But it is not hard to create one from scratch.

Here is one example how to create a simple hexdump utility in …

Case statements in Ada (video)

Jacob Sparre Andersen — Sat, 01 Aug 2015 18:00:00 +0300

Case statements and compile-time coverage checking Ada

Create multiple instances of same package using parameterless generics

Tero Koskinen — Fri, 10 Jul 2015 17:00:00 +0300

There are some cases when you want to create and use multiple instances of same package.

This is easily done by creating a generic package which does not take any parameters:

generic
package Counter is
   function Get_Number return Natural;
end Counter;

package body Counter is
   Counter_Value : Natural := 0;

   function Get_Number …

Use Ada 2012 aspects to specify variable locations

Tero Koskinen — Fri, 16 Jan 2015 23:00:00 +0200

Earlier with Ada 95 and Ada 2005, if you wanted to put a variable to some specific memory location, you had to use 'for Variable'Address use X' statement and Volatile pragma for that:

My_Var : Unsigned_32;
for My_Var'Address use System'To_Address (16#FF00#);
pragma Volatile (My_Var);

With Ada 2012 this becomes simpler …

Using quotation mark easily in Strings

Tero Koskinen — Sat, 11 Oct 2014 16:00:00 +0300

Did you know that you can easily use quotation marks inside String literals by typing the quotation mark twice?

Example:

Put_Line ("Hello, ""anonymous"" person!");

Self-referencing Objects

Jacob Sparre Andersen — Thu, 21 Aug 2014 08:00:00 +0300

One may in some cases want an object to contain a reference ('Access) to itself.

The package Self_Referencing_Objects shows how one can implement (consistently) self-referencing objects using limited records and discriminants.

type Instance is limited private;
...
type Holder (Reference : access Instance) is limited null record;
type Instance is limited
   record …

Using discriminated records to return variable amount of data from function

Tero Koskinen — Tue, 12 Aug 2014 23:45:00 +0300

Sometimes, you want to return different data from a function dependending on the given parameters and the program state. For example, when searching a container for a certain element, you either want to return "NOT_FOUND" information or the actual element.

One way to do this is to use discriminated (or …

Easy way to create portable bindings to opaque C types

Tero Koskinen — Tue, 06 May 2014 21:45:00 +0300

Have you ever struggled to create bindings for C types like FILE or CURL? If yes, then you know how hard it can be, since the type might not be same on all platforms.

Easy solution for these is to define a null record which represents the type and use …

Checking file header with Adacontrol

Tero Koskinen — Thu, 27 Mar 2014 22:30:00 +0200

Many times you want to make sure that your code has correct comment block at the beginning of the source code file. This comment block can contain the source code license, copyright information, the name of the author, or description of the file.

Adacontrol can help you here with its …

Redirecting Text_IO output to a file

Tero Koskinen — Fri, 14 Mar 2014 22:30:00 +0200

One, probably not so often used, feature of Ada.Text_IO is an ability to redirect output (Put, Put_Line, Newline) to a file. It happens simply by opening a file where you want to redirect the output and then calling Set_Output procedure.

Example below shows how it is done:

with Ada …

Checking "out" parameters with Adacontrol

Tero Koskinen — Sat, 08 Mar 2014 21:45:00 +0200

Have you ever accidentally written code like this?

procedure Example_Proc (X : out Boolean) is
begin
   null; -- Do something, but do not touch X
end Example_Proc;

with Example_Proc;
procedure Main is
   My_Flag : Boolean;
begin
   Example_Proc (My_Flag);
end Main;

In the above code, parameter X with mode "out" is left untouched. Because …

Opening a web page using default browser with Ada on Windows

Tero Koskinen — Mon, 03 Mar 2014 23:00:00 +0200

Open a web page on Windows using Ada