Stuck on an Ada Program - Stuck on Input

Question

I have a pretty simple Ada project on my hands. The task is to take a collection of a \"voter\'s\" votes and compare it to each \"candidate\'s\" score and determine which ca

Answer 1

Because the number of rows is given in the file, a constrained array has to be large enough to hold all possible elements. Instead, you can declare an unconstrained array:

subtype Voter_Index is Positive range 1 .. 10;
type Voter_Array is array(Voter_Index) of Integer;
type Candidate_Array is array(Character range <>) of Voter_Array;

Later, when you know the actual count, you can allocate only the space actually required for the array. This declaration puts Candidates on the stack in a nested scope:

Number_Of_Candidates := ...;
declare
   Candidates : Candidate_Array(
      'A' .. Character'Val(Character'Pos('A') + Number_Of_Candidates));
begin
   ...
end;

Alternatively, you can allocate space on the heap:

type Candidate_Array_Ptr is access Candidate_Array;
Candidates: Candidate_Array_Ptr;

begin
   Number_Of_Candidates := ...;
   Candidates := new Candidate_Array(
     'A' .. Character'Val(Character'Pos('A') + Number_Of_Candidates));
end;

In either case, you can access the array elements as required:

for i in Candidates'Range loop
   for j in Voter_Array'Range loop
      Ada.Integer_Text_IO.put(Candidates(i)(j), 5);
   end loop;
   Ada.Text_IO.New_Line;
end loop;

Addendum: This approach assumes that candidate names are consecutive Characters. As an alternative, consider an array of Candidate_Record, where each Name is read from the file:

type Candidate_Record is
   record
      Name  : Character;
      Votes : Voter_Array;
   end record;
type Candidate_Array is array(Positive range <>) of Candidate_Record;

Candidates : Candidate_Array(1 .. Number_Of_Candidates);

for i in Candidates'Range loop
   Ada.Text_IO.Put(Candidates(i).Name & ':');
   for j in Voter_Array'Range loop
      Ada.Integer_Text_IO.Put(Candidates(i).Votes(j), 5);
   end loop;
   Ada.Text_IO.New_Line;
end loop;

Answer 2

You could use streams in order to read the data in: Integer'Read( STREAM_HANDLE, VARIABLE )

Another option is reading the values via Get for each element of your array, I'd recommend a helper-function in case you need to tweak the procedure for handling format changes:

    Function  Get_Vote ( File  : File_Type ) Return Integer is
    begin
        Return Result : Integer do
            Integer_IO.Get(
                File  => File,
                Item  => Result
               );
        End return;
    end Read_Votes;

and

For Index in VOTE_ARRAY'range loop
    VOTE_ARRAY( Index ) := Get_Vote( INPUT_FILE );
End loop;