ADA 2005: sorting constrained array

Mario Blunk · 01-28-2014, 10:31 AM

Does anyone have an example of how to sort a constrained array in ADA (2005) ?

I found an example for an unconstrained array here

http://rosettacode.org/wiki/Sort_an_...structures#Ada

But I could not manage to adopt it to a constrained array as shown in the code below. GNAT says regarding the line marked below:
"guv.adb:744:55: index types of actual do not match those of formal "Array_Type"
guv.adb:744:55: instantiation abandoned
gnatmake: "guv.adb" compilation error

Code:

procedure sort_bookings 
	( takings_to_sort : takings_sized) is -- a constrained array gets passed

	function "<" (L, R : entry_taking) return Boolean is
	 begin
	  return L.date < R.date;
	 end "<";
				
	procedure Put_Line (C : entry_taking) is
	 begin
	  Put_Line (C.date & " " & to_string(C.subject));
	end Put_Line;
				
	procedure Sort is new Ada.Containers.Generic_Constrained_Array_Sort (
		index_type => natural, 
		element_type => entry_taking, 
   	        array_type => takings_sized -- <-- affected line
                );

	begin
	--Sort (expenses);
	-- for I in 1..expenses'last loop
	-- 	Put_Line (expenses (I));
	-- end loop;
	end sort_bookings;

Thanks for your help !!!

muggabug · 02-10-2014, 05:10 PM

Ada generics are way over my head, but I think that your only problem is that you have defined the wrong type or bounds for the array index somewhere.

Running a little test with different index types in definition and declaration for a generic function, causes a similar error message from gnat-ada95:

h.adb:13:42: index types of actual do not match those of formal "arT"
h.adb:13:42: instantiation abandoned

Code used:

Code:

function h return integer is
   subtype r is natural range 1..20;
   generic
      type item is (<>);
      type arT is array(r) of item;
      function print(x:in arT) return string;
      function print(x:arT) return string is
      begin
         return "nothing";
      end print;
      type tmp is array(natural range 1..21) of character;
      function f is new print (character,tmp);
begin
   return 0;
end h;

Looks like this is it

--------
(If anyone has a clue about this, why, btw, can't I just use:
type arT is array(natural range 1..20) of item;
This gives me an error
(error is p.adb:5:25: only a subtype mark is allowed in a formal)
but would be much simpler, just like substituting the type definition for tmp in the "..new print.." declaration somewhere.)