Re: Fractional part of decimal value.

Hi Paulo,

Thanks for the response! The functions that you mention have the same
outcome:
~~~
?- X is float_fractional_part(1.1).
X = 0.10000000000000009.
~~~
Even:
~~~
?- X is 1.1 - 1.
X = 0.10000000000000009.
~~~
I understand that most decimal fractions cannot be represented by binary
fractions, so there is probably a good reason to have the '9' appear at the
end.

My question is whether this can be circumvented for my simple/naive use.
(Preferably a solution that does not involve a hack such as using
format-to-codes and then number_codes/2 :-P.)

---
Cheers!,
Wouter.

E-mail: [email protected]
WWW: www.wouterbeek.com
Tel.: 0647674624


On Wed, Aug 7, 2013 at 4:21 PM, Paulo Moura <[email protected]> wrote:

>
> On 07/08/2013, at 15:14, Wouter Beek <[email protected]> wrote:
>
> > Hi all,
> >
> > I want to extract the integer and fractional part of a decimal value:
> > ~~~{.pl}
> > decimal_parts(D, I, F):-
> >  I is floor(D / 1),
> >  F is D - I * 1.
> > ~~~
> > What I get is the fractional part of the float value 1.1:
> > ~~~
> > ?- decimal_parts(1.1, _, F).
> > F = 0.10000000000000009.
> > ~~~
> > I do not mind the padding zero's (just a notational difference), but I do
> > not need the 9 at the end.
> >
> > Is there a way to get the same result as with e.g. C's modf (sample code
> > below)? Thanks for any suggestions!
> >
> > ---
> > Cheers,
> > Wouter.
> >
> > Sample code in C:
> > ~~~{.c}
> > #include <stdio.h>
> > #include <math.h>
> >
> > int main() {
> >  double param, fractional_part, integer_part;
> >  param = 1.1;
> >  fractional_part = modf(param, &integer_part);
> >  printf("%f = %f + %f \n", param, integer_part, fractional_part);
> >  return 0;
> > }
> > ~~~
> >
> > Compile and run:
> > ~~~
> > $ gcc -Wall test.c -o test
> > $ ./test
> > 1.100000 = 1.000000 + 0.100000
> > ~~~
>
>
> I assume that you're aware of the float_integer_part/1 and
> float_fractional_part/1 ISO Prolog standard functions but for some reason
> you found them not adequate for your task?
>
> Cheers,
>
> Paulo
>
>
> -----------------------------------------------------------------
> Paulo Moura
> Logtalk developer
>
> Email: <mailto:[email protected]>
> Web:   <http://logtalk.org/>
> -----------------------------------------------------------------
>
>
>
>
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