Ada input from a terminal

General
34

First off, please format code when posting, for blocks use three back-ticks (```) to bracket the block (on their own line); for a inline, use single backticks to bracket the item.
Secondly, the difference is obvious once you understand unconstrained arrays, the simple way to explain it being “X :String;” is rejected by the compiler because it doesn’t know the length, while “X : String := "Hello";” takes the length from the initialization to specify the length, and similarly “X : String:= Get_Line;” uses the function’s result to perfectly size the buffer (String) to the value it receives. (See Memory Management with Ada 2012. linked below.)

You can even combine having a buffer with returning long strings via recursively calling a buffered function; as shown in this Adapower.com example:

function Next_Line(File : in Ada.Text_IO.File_Type :=
   Ada.Text_Io.Standard_Input) return String is
   Answer : String(1..256);
   Last   : Natural;
begin
   Ada.Text_IO.Get_Line(File => File,
      Item => Answer,
      Last => Last);
   if Last = Answer'Last then
      return Answer & Next_Line(File);
   else
      return Answer(1..Last);
   end if;
end Next_Line;

PS — J.P. Rosen’s excellent presentation: Memory Management with Ada 2012.

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