Ada95 Loop through Array within a Record and print the characters

Question

The program below is suppose to get an input of Characters from the user and put it into an Record with the subprogram Procedure Get(Tecken : out Record_Type). The last step is to Print it in the Terminal with another subprogram Procedure Put(Chars : in Chars_Array).

The issue I'm facing is the actual output of the Characters into the Terminal where I get:

Picture of the Output

procedure Poster is

type Char_Array is                            -- Fält/Array
    array (1..256) of Character;

type Record_Type is                           -- Post/Record
    record
        Chars : Char_Array;
        Length : Integer;
    end record;

procedure Get(Tecken : out Record_Type) is   -- Character input

begin

    for I in 1..256 loop
        Get(Tecken.Chars(I));
        exit when End_Of_Line;
    end loop;

end Get;

Here is the subprogram that prints the Characters from the Array. I'm confused when it comes to Records and Arrays, but I'm thinking that I need an Array as a inparameter since I can't loop through Records.

procedure Put(Chars : in  Char_Array) is   -- Character output

begin

    for I in 1..256 loop
        Put(Chars(I));
    end loop;

end Put;

Here is another bump in the road where I use an inparameter "Chars" the Put-Call. Does the Char_Array recognize the input in "Tecken" ?

Tecken : Record_Type;
Chars : Char_Array; 

begin

    Get(Tecken);
    Put(Chars);

end Poster;

Do you fill out all the positions in `Tecken.Chars` in procedure `Get`? — Jacob Sparre Andersen, Oct 29 '17 at 11:35
It all depends on the user. I've added "exit when End_Of_Line;" to determine if there is an Enter pressed. I have only tried random input such as "asdfg" to se what output I recieve. — R.Englund, Oct 29 '17 at 11:42
In what way do you ensure that you don't attempt to output more with `Put` than what was read by `Get`? — Jacob Sparre Andersen, Oct 29 '17 at 11:55
This looks liike you really want to use `Ada.Strings.Bounded` with a `Max` of 256. — flyx, Oct 29 '17 at 12:10

Simon Wright · Answer 1 · 2017-10-29T15:56:28.297

There’s a bit of a warning from the compiler:

poster.adb:31:04: warning: variable "Chars" is read but never assigned

This is because Get writes to Tecken.Chars; the Chars you pass to Put has nothing to do with it, and is filled with random data.

You say "I'm thinking that I need an Array as a inparameter since I can't loop through Records". True, you can’t loop through a record, but you can loop through an array that is part of a record.

If you say

Put(Tecken.Chars);

things work better, though you still get garbage after the actual input. You might expect even better if you say

   Put(Tecken.Chars (1 .. Tecken.Length));

but

$ ./poster 
0123456789

raised CONSTRAINT_ERROR : poster.adb:36 range check failed

which is because Get doesn’t actually set Tecken.Length.

After fixing this[*], this should do the trick

procedure Put (Tecken : in  Record_Type) is
begin
   for I in 1 .. Tecken.Length loop
      Put (Tecken.Chars(I));
   end loop;
end Put;

Now, the call is just

Put (Tecken);

[*] It’s not as easy to fix Get as you might hope, since when End_Of_Line is true the character returned is the last one on the line.

When I add Put(Tecken.Chars(1..Tecken.Length)) to the call, and the subprogram to "procedure Put(Tecken : in Record_Type) is begin — R.Englund, Oct 29 '17 at 15:33
Ignore the above comment. I added the things to told me to in both the Call and inside the subprogram but I get the Error-messages: "expected type "Record_Type" defined at line 9" "found type "Char_Array" defined at line 6" The compiler is complaining about Record_Type, and Tecken.Chars is clearly a Record_Type, or am I wrong? — R.Englund, Oct 29 '17 at 15:44
After altering the definition of `Put`, the call should just be `Put (Tecken);`. `Tecken` is a `Record_Type`, and `Tecken.Chars` is a `Char_Array`. — Simon Wright, Oct 29 '17 at 15:54

Ada95 Loop through Array within a Record and print the characters

1 Answers1