guideline

Use the predefined packages for string handling.

Writing code such as the following is no longer necessary in Ada 95:

function Upper_Case (S : String) return String is

   subtype Lower_Case_Range is Character range 'a'..'z';

   Temp : String := S;
   Offset : constant := Character'Pos('A') - Character'Pos('a');

begin
   for Index in Temp'Range loop
      if Temp(Index) in Lower_Case_Range then
         Temp(Index) := Character'Val (Character'Pos(Temp(Index)) + Offset);
      end if;
   end loop;
   return Temp;
end Upper_Case;


with Ada.Characters.Latin_1;
function Trim (S : String) return String is
   Left_Index  : Positive := S'First;
   Right_Index : Positive := S'Last;
   Space : constant Character := Ada.Characters.Latin_1.Space;
begin
   while (Left_Index < S'Last) and then (S(Left_Index) = Space) loop
      Left_Index := Positive'Succ(Left_Index);
   end loop;

   while (Right_Index > S'First) and then (S(Right_Index) = Space) loop
      Right_Index := Positive'Pred(Right_Index);
   end loop;

   return S(Left_Index..Right_Index);
end Trim;

Assuming a variable S of type String, the following expression:

Upper_Case(Trim(S))

can now be replaced by more portable and preexisting language-defined operations such as:

with Ada.Characters.Handling;  use Ada.Characters.Handling;
with Ada.Strings;              use Ada.Strings;
with Ada.Strings.Fixed;        use Ada.Strings.Fixed;

...
To_Upper (Trim (Source => S, Side => Both))

rationale

The predefined Ada language environment includes string handling packages to encourage portability. They support different categories of strings: fixed length, bounded length, and unbounded length. They also support subprograms for string construction, concatenation, copying, selection, ordering, searching, pattern matching, and string transformation. You no longer need to define your own string handling packages.