Newbie: Ada function like C++'s atoi?

Newbie: Ada function like C++'s atoi?

[Keith C. McCready]

Greetings,

I am a college student taking an introductory Ada programming class who is
familiar with C/C++.  Looking for Ada function similar to atoi.  Purpose: I
want the following to raise an exception when the user enters a floating
point value.  Right now, if the user enters a value of 3.1415, the value
received by the Get is 3.

I would like to read the user input as a character string, convert and
validate that the string is an integer value within the range of
Percent_Type.

*************************
-- subtypes
subtype Percent_Type is Integer range 0..100;

-- variables:
Percent    : Percent_Type;

-- procedures:
procedure Check_Percent ( Percent  : out Percent_Type ) is

begin -- Check_Percent
    Validation_Loop:
      loop

        Percent_Validation_Block:
        begin
            Integer_IO.Get ( Item => Percent );
            exit Validation_Loop;

            exception
                 when CONSTRAINT_ERROR =>
                      Text_IO.Put ( Item => "Valid range is 0 to 100" );
                      Text_IO.New_Line;
                      Text_IO.Skip_Line;

                 when others =>
                      Text_IO.Put ( Item => "Enter an integer value of 0 to
100:  " );
                      Text_IO.New_Line;
                      Text_IO.Skip_Line;
       end Percent_Validation_Block;

  end loop Validation_Loop;

end Check_Percent;

******************

Thanks for any suggestions or comments,

Keith C. McCready

mccreak9708@uni.edu

kmccready@agweb.com

Re: Newbie: Ada function like C++'s atoi?

[Vincent Marciante]

You are using Integer_IO's get.
One of the other standard ..._IO packages provides the facilities that
you want.

Re: Newbie: Ada function like C++'s atoi?

[Robert Dewar]

In article <38e17eab@news.siscom.net>,
  "Keith C. McCready" <kmccready@agweb.com> wrote:

You pretty much solved your own problem

> I would like to read the user input as a character string

OK, that should be easy for you to find out how to do, since
you know about Text_IO, it is pretty easy to find the Get
that works on strings.

> convert and
> validate that the string is an integer value within the range
> of Percent_Type.

This is a little harder to find. The clue is that it is related
to a specific subtype, and such subtype related functions appear
as either operators or attributes (not functions, since clearly
there could not be a library function that knew about your
Percent_Type in advance).

So look through the attributes and you will find 'Value, and
low and behold, Percent_Type'Value is *exactly* what you are
looking for :-)

P.S. are you sure you want Percent_Type to be a subtype of
Integer, seems like a bad idea to me. Indeed a pretty general
rule in Ada is never to use the type Integer. Instead you
probably want

   type Percent_Type is range 0 .. 100;

This will prevent you from a mistake like

   X : Integer;
   Y : Percent_Type;

   --  Compute Y percent of X

   X := Y * X;

Now an ordinary multiplication here is complete nonsense. With
your declaration, it won't get caught, but with my declaration
above, this will be legal. You could even declare

   function "*" (A : Integer; B : Percent_Type) return Integer;

that does the "right" thing and allows the above assignment
resulting in the intended effect.




>
> *************************
> -- subtypes
> subtype Percent_Type is Integer range 0..100;
>
> -- variables:
> Percent    : Percent_Type;
>
> -- procedures:
> procedure Check_Percent ( Percent  : out Percent_Type ) is
>
> begin -- Check_Percent
>     Validation_Loop:
>       loop
>
>         Percent_Validation_Block:
>         begin
>             Integer_IO.Get ( Item => Percent );
>             exit Validation_Loop;
>
>             exception
>                  when CONSTRAINT_ERROR =>
>                       Text_IO.Put ( Item => "Valid range is 0
to 100" );
>                       Text_IO.New_Line;
>                       Text_IO.Skip_Line;
>
>                  when others =>
>                       Text_IO.Put ( Item => "Enter an integer
value of 0 to
> 100:  " );
>                       Text_IO.New_Line;
>                       Text_IO.Skip_Line;
>        end Percent_Validation_Block;
>
>   end loop Validation_Loop;
>
> end Check_Percent;
>
> ******************
>
> Thanks for any suggestions or comments,
>
> Keith C. McCready
>
> mccreak9708@uni.edu
>
> kmccready@agweb.com
>
>


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