Re: Easy way to read FLOAT?

[spiegel@bruessel.informatik.uni-stuttgart.de (Andre Spiegel)]

In article <3gaihr$hak@pdq.coe.montana.edu> icsjp318@gemini.oscs.montana.edu (Aaron Diesen) writes:

> I am working on my first ada program, and I need to read a float.  I ran 
> into problems when trying to input an integer into a float variable 
> (works in other languages). [...] 

Has to do with what I have been working on just recently, it's also been
discussed here in this group. I'm not sure if I understand your
question correctly. Let me take it that you want to read some input and you
don't know whether you are looking at an integer or a float literal.

In your program, the corresponding variable should definitely be a
float (because float values are, roughly speaking, a superset of
integer values). First, you should read your input into a
string. Easiest way to do that: use Text_IO.Get_Line and work with the
resulting string furtheron, let's call it `Line'.

You can then try to interpret the string as a float literal. If that fails,
because it's an integer literal (i.e. there's no decimal point, etc.), 
Data_Error will be raised, and you can give it a second try by trying 
to read it as an integer:

  declare
    Val : Float;
  begin
    Get (Line (1..Last), Val, Index);
  exception
    when Data_Error =>
      declare 
        Int_Val : Integer;
      begin
        Get (Line (1..Last), Int_Val, Index);
        Val := Float (Int_Val);
      exception
        when Data_Error =>
          raise;  -- no, it wasn't an Integer either
      end;
  end;

This fails, of course, for very large "Integer" values, which is the
reason why I wrote that I/O package I talked about the other day. If
large values are a problem for you, send me e-mail.

Have I done someone's homework now? ;-)

Regards,

--
Andre Spiegel                     |  This life is a test. It is only a test.
                                  |  Had this been an actual life, you would
University of Stuttgart, Germany  |  have received further instructions as to
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	   email: spiegel@bruessel.informatik.uni-stuttgart.de