Re: fixed type (delta) in ada

[Robert Dewar <robert_dewar@my-deja.com>]

In article <383f6dbb.22609744@news.tstonramp.com>,
  nap@nobody.com (Nap) wrote:
> does anyone know why mutiplication between fixed type in ada
produce a
> big round off error?
>
> type money is delta 0.01 range 0.0..100_000_000.00;
> a, b, c : money;
>
> package money_io is new ada.text_io.fixed_io(money);
>
> a := 351.00;
> b := 0.20;
> c := a * b;
>
> money_io.put(c);
>
> -- the output should be 70.2 but it prints 71.3 instead.
> -- this is so frustrating. typecasting (back to float) doesn't
help
> either.


No, the output should be 71.3, and this is what is expected. You
used a binary fixed point type, so you are working with binary
numbers not decimal numbers. You need to read up more on the
details of how fixed point works, or indeed you will frustrated
yourself! Most likely you should be using decimal types (look
up decimal types in the RM or in any good Ada text book).


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