"&" for array versus "&" for Strings

[Preben Randhol <randhol+news@pvv.org>]

According to the ARM 4.5.3:

  3. The concatenation operators & are predefined for every nonlimited,
     one-dimensional array type T with component type C. They have the
     following specifications:

  4.      function "&"(Left : T; Right : T) return T
          function "&"(Left : T; Right : C) return T
          function "&"(Left : C; Right : T) return T
          function "&"(Left : C; Right : C) return T

If I use this in this way:

------------------------------------------------------------------
with Ada.Text_IO; use Ada.Text_IO;
procedure Array_Test is

   type Name_Array is array (Positive range <>) of String (1..6);

   procedure Print_Names (Names : Name_Array) is
   begin
      for No in Names'First .. Names'Last loop
         Put_Line (Integer'Image(No) & ": " & Names (No));
      end loop;
   end;

begin

   Print_Names ("Ada   " & "Babbel");

end Array_Test;
------------------------------------------------------------------

Then the result becomes:


 1: A 2: d 3: a 4:   5:   6:   7: B 8: a 9: b 10: b 11: e 12: l
Why is this happening.

If I do :

Print_Names ("Ada   " & "Babbel" & "Odin  ");

gnatmake array_test.adb 
gnatgcc -c array_test.adb
array_test.adb:15:26: ambiguous operand for concatenation
array_test.adb:15:26: possible interpretation at line 4
array_test.adb:15:26: possible interpretation in package Standard
gnatmake: "array_test.adb" compilation error

which is expected.

and 

Print_Names ("Ada   Babbel");

gnatmake array_test.adb 
gnatgcc -c array_test.adb
array_test.adb:15:17: expected type "Name_Array" defined at line 4
array_test.adb:15:17: found a string type
gnatmake: "array_test.adb" compilation error

which is also expected.


-- 
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http://libre.act-europe.fr/Software_Matters/02-C_pitfalls.pdf