Re: Something I don't understand

[adambeneschan@gmail.com]

On Thursday, February 13, 2014 3:57:58 PM UTC-8, Laurent wrote:
> Hi
> 
> 
> 
> Doing an exercise from the book "Ada 95 Problem Solving and Program Design".
> 
> I am supposed to make a robust function to read some values. It works so far but there is one thing I don't
> 
> understand.
 
>    MaxName : CONSTANT Positive := 30; -- defined in other package 
>    SUBTYPE NameType IS String (1 .. MaxName); -- defined in other package
> 
>    Count : Natural RANGE 1.. MaxName;
>
>          Name : LOOP
>                BEGIN --exception handler block               
>                     Ada.Text_IO.Put ("Name (1 - ");
>                     Ada.Integer_Text_IO.Put (Item => MaxName,Width => 1);
>                     Ada.Text_IO.Put(Item => " characters) >");
>                     Ada.Text_IO.Get_Line (Item => S, Last => Count);
>                     Item.Name (1 .. Count) := S (1 .. Count);  
>                     Ada.Text_IO.Skip_Line;
> 
>                EXIT; -- correct Name
> 
>             EXCEPTION
>                WHEN Constraint_Error =>
>                   Ada.Text_IO.Skip_Line;
>                   Ada.Text_IO.Put (Item => "Name too short/long!");
>                   Ada.Text_IO.New_Line;
> 
>             END; -- exception handler
> 
>          END LOOP Name;
> 
> 
> 
> 
> 
> So when I enter nothing as name I get a Constraint_Error which is handled. That's ok but when the name I enter is longer than 30 chars no exception. Is that normal and if yes/no why? 

Yes, because that's how the *procedure* Get_Line is defined.  It stops reading when it reaches the end of the string, or the end of the line.  (RM A.10.7(18-20))

If you want to check for input that is too long, you can use the *function* Get_Line, which always reads to the end of the line:

    declare
        Input : String := Ada.Text_IO.Get_Line;
    begin
        if Input'Length <= NameType'Length then
            Item.Name (1 .. Input'Length) := Input;
            --Ada.Text_IO.Skip_Line;  --you shouldn't need this, Get_Line will
                                      --automatically perform this
            exit Name;  -- correct name
        else
            Ada.Text_IO.Put_Line (Item => "Name too long!");
            -- combination of Put and New_Line
        end if;
    end;  -- this ends the block starting with "declare"

                            -- Adam