ada split() method

Question

I am trying to write an Ada equivalent to the split() method in Java or C++. I am to intake a string and an integer and output two seperate string values. For example: split of "hello" and 2 would return: "The first part is he and the second part is llo"

The code I have is as follows:

-- split.adb splits an input string about a specified position.
--
-- Input: Astring, a string,
--        Pos, an integer.
-- Precondition: pos is in Astring'Range.
-- Output: The substrings Astring(Astring'First..Pos) and
--                        Astring(Pos+1..Astring'Last).
--------------------------------------------------------------

with Ada.Text_IO, Ada.Integer_Text_IO, Ada.Strings.Fixed;
use  Ada.Text_IO, Ada.Integer_Text_IO, Ada.Strings.Fixed;

procedure Split is

   EMPTY_STRING : String := "                                        ";

   Astring, Part1, Part2 : String := EMPTY_STRING;
   Pos, Chars_Read       : Natural;

   ------------------------------------------------
   -- Split() splits a string in two.           
   -- Receive: The_String, the string to be split,
   --          Position, the split index.        
   -- PRE: 0 < Position <= The_String.length(). 
   --     (Ada arrays are 1-relative by default)
   -- Passback: First_Part - the first substring,
   --           Last_Part - the second substring.
   ------------------------------------------------
   function Split(TheString : in String ; Pos : in Integer; Part1 : out String ; Part2     : out String)  return String is 
   begin
    Move(TheString(TheString'First .. Pos), Part1);
    Move(TheString(Pos .. TheString'Last), Part2);
    return Part1, Part2;
     end Split;



begin                                           -- Prompt for input
   Put("To split a string, enter the string: ");
   Get_Line(Astring, Chars_Read);
   Put("Enter the split position: ");
   Get(Pos);

   Split(Astring, Pos, Part1, Part2);

   Put("The first part is ");
   Put_Line(Part1);
   Put(" and the second part is ");
   Put_Line(Part2);

end Split;

The main part I am having trouble with is returning the two separate string values and in general the whole split() function. Any pointers or help is appreciated. Thank you

Answer 1

Doing this is so trivial, I'm not sure why you'd bother making a routine for it. Just about any routine you could come up with is going to be much harder to use anyway.

Front_Half : constant String := Original(Original'first..Index);
Back_Half  : constant String := Original(Index+1..Original'last);

Done.

Note that static Ada strings are very different than strings in other languages like C or Java. Due to their static nature, they are best built either inline like I've done above, or as return values from functions. Since functions cannot return more than one value, a single unified "split" routine is just plain not a good fit for static Ada string handling. Instead, you should either do what I did above, call the corresponding routines from Ada.Strings.Fixed (Head and Tail), or switch to using Ada.Strings.Unbounded.Unbounded_String instead of String.

The latter is probably the easiest option, if you want to keep your Java mindset about string handling. If you want to really learn Ada though, I'd highly suggest you learn to deal with static fixed Strings the Ada way.