Re: New to Ada need help implementing Warshall's algorithm

[Simon Wright <simon@pushface.org>]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> On Friday, September 23, 2016 at 10:07:53 AM UTC-5, James Brewer wrote:
>> 
>> It is three diffent sets of data. I think I may try to simplify the
>> input data to a 0,1 2d array for each set, read the set in and then
>> process each set writing it to an output file (the last two I will
>> have to figure out).
>
> Here's a working program that does the IO, to get you started. It
> reads from a file, writes to standard out.

And here's a different one, which works out the size of the matrix by
finding the number of unique names in the input. The structure supports
strings for names, but the implementation only handles single-character
names because I was being lazy.

Input:
e b
a b
b c
b d
d a
d e
c e

Output:
a  3
b  2
c  4
d  5
e  1
01000
00011
01000
10000
10100

Code:
with Ada.Command_Line;
with Ada.Containers.Indefinite_Ordered_Maps;
with Ada.Text_IO; use Ada.Text_IO;

procedure Brewer is

   File : File_Type;

   package Names_To_Indices
     is new Ada.Containers.Indefinite_Ordered_Maps (String, Positive);
   Names : Names_To_Indices.Map;

   procedure Add_If_New (Name : String)
   is
      use type Ada.Containers.Count_Type;
   begin
      if not Names.Contains (Name) then
         Names.Insert (Name, Positive (Names.Length + 1));
      end if;
   end Add_If_New;

begin

   Open (File, In_File, Ada.Command_Line.Argument (1));
   --  each line is to have format Name_1 Name_2, implying there is a
   --  path from Name_1 to Name_2.

   loop
      begin
         declare
            Line : constant String := Get_Line (File);
         begin
            --  I'm being lazy here and assuming single-character Names.
            Add_If_New (Line (1 .. 1));
            Add_If_New (Line (3 .. 3));
         end;
      exception
         when others => exit;
      end;
   end loop;
   Reset (File);

   --  output name-to-index (ordered by name, not index, sorry)
   for J in Names.Iterate loop
      Put_Line (Names_To_Indices.Key (J)
                  & " "
                  & Names_To_Indices.Element (J)'Img);
   end loop;

   --  now we know the size of the matrix
   declare
      Size : constant Positive := Positive (Names.Length);
      Matrix : array (1 .. Size, 1 .. Size) of Boolean
        := (others => (others => False));
   begin
      --  populate the matrix
      loop
         begin
            declare
               Line : constant String   := Get_Line (File);
               From : constant Positive := Names.Element (Line (1 .. 1));
               To   : constant Positive := Names.Element (Line (3 .. 3));
            begin
               Matrix (From, To) := True;
            end;
         exception
            when others => exit;
         end;
      end loop;
      Close (File);

      --  dump the matrix
      for J in Matrix'Range (1) loop
         for K in Matrix'Range (2) loop
            Put (if Matrix (J, K) then '1' else '0');
         end loop;
         New_Line;
      end loop;
   end;

end Brewer;