There is indeed an easy way to do this in Ada (quite similar to the way you would do the same thing in C!):
with Ada.Numerics;
with Ada.Text_IO; use Ada.Text_IO;
procedure Floating_Conversion is
D : constant Long_Float := Ada.Numerics.Pi;
F : Float;
begin
F := Float (D); -- The conversion!
Put_Line ("double:" & Long_Float'Image (D));
Put_Line ("single:" & Float'Image (F));
end Floating_Conversion;