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From Eric Barnhill <ericbarnh...@gmail.com>
Subject Re: [commons-numbers] [...] NUMBERS-91: Added ofInt() factory methods [...]
Date Mon, 14 Jan 2019 23:41:00 GMT
I think you make some good points here. Why call the "straightforward"
factory method ofInt when there is no reason not to use a long, or
BigInteger (or I suppose byte). These could all be handled with the
overloaded factory method of(). For Fraction, it is probably reasonable to
have only int-based constructors, but BigFraction should IMO take ints,
longs, or BigIntegers.

Similarly, the decimal case requires conversion, iteration and estimation.
I don't think there are scenarios under which it fails, but if the rounding
criterion were too strict, it would be unlikely to deliver what the user
wants (e.g. submitting .142857 but rounding to the first decimal place). So
Fractions with decimal input could be covered by the overloaded factory
method from() .

So just of() and from(), I think we could get a three person consensus on
this! :)

Eric

On Fri, Dec 28, 2018 at 10:34 AM Gilles <gilles@harfang.homelinux.org>
wrote:

> On Fri, 28 Dec 2018 09:17:08 -0800, Eric Barnhill wrote:
> > Fractions are constructed using either ints or doubles. In the case
> > of
> > ints, the numerator and denominator are passed (or the denominator is
> > assumed to be one). Constructing fractions from doubles is more
> > algorithmic
> > work: if I pass a known fixed quantity such as 0.6 of course it will
> > not be
> > hard for the constructor to determine that is the equivalent of 3 / 5
> > .
> > However if doubles are being passed of unknown precision, then I may
> > want
> > to request a max value on the denominator, or a precision within
> > which the
> > simplest fraction should be returned, or even the maximum iterations
> > in the
> > computation.
> >
> > I think of those as qualitatively very different activities
>
> I agree.
>
> > so I called
> > them ofInt and ofDouble.
>
> But we could consider:
> Cat.1
>   * of(long, long)
>   * of(int, long)
>   * of(BigInteger, BigInteger)
>   * ...
> and
> Cat.2
>   * ofDouble(double)
>   * ofDouble(int, double)
>   * ...
> where "Cat.1" and "Cat.2" delineates the very different handling
> which you referred to; and in the case of "Cat.1", an exact (?)
> representation is constructed, while "Cat.2" could be lossy.
> The former can also be construed as closer to the convention for
> "ValJO" ("BigFaction" not being "ValJO" does not preclude choosing
> the simplest name for its factory methods).
>
> > The example I had in mind was probably Complex,
> > where we have ofPolar and ofCartesian. I suppose you are right, in
> > this
> > case the hard typing of the passed variables alone could invoke
> > either an
> > int or double based method while with Complex, both constructors are
> > taking
> > doubles.
>
> Quite right, there is some inconsistency; we may consider using
> "of" if the "ValJO" aspect is more important that the equivalence
> between polar and Cartesian input (cf. also the suggestion that
> conversion methods should be name "from...", to which I'm not really
> a fan yet).
> If there is no strong argument yet for either, we could open a JIRA
> report asking for opinions.  And leave that open as long as we
> release "beta" versions.
>
> > You do then have some very similar methods, for example of(int a, int
> > b)
> > will be an integer fraction with a on top and b on bottom; while
> > calling
> > of(double a, int b) will produce a fraction that approximates double
> > a with
> > max denominator b.
> >
> > Those two processes are so different that it might be more clarifying
> > to
> > distinguish them as ofInt(int a, int b) and ofDouble(double a, int b)
>
> IMHO, it is not sufficiently self-documenting anyway: one has to go
> to the docs in order to understand the difference; hence my proposal
> to have "of" for the "obvious thing" (a/b) and "ofDouble" for the more
> elaborate "transform".
> Not sure if I'm clear in why the "non-symmetric" makes sense. :-}
>
> Best regards,
> Gilles
>
> >
> > Eric
> >
> >
> > On Fri, Dec 28, 2018 at 4:33 AM Gilles <gilles@harfang.homelinux.org>
> > wrote:
> >
> >> Hello Eric.
> >>
> >> On Thu, 27 Dec 2018 17:00:15 -0800, Eric Barnhill wrote:
> >> > I am overloading:
> >> >
> >> > public static BigFraction ofInt(final BigInteger num) {
> >> >         return new BigFraction(num, BigInteger.ONE);
> >> >     }
> >> >
> >> >     public static BigFraction ofInt(BigInteger num, BigInteger
> >> den) {
> >> >     return new BigFraction(num, den);
> >> >     }
> >> >
> >> >     private BigFraction(BigInteger num, BigInteger den) {
> >> >
> >> > Did my comment not give that impression?
> >>
> >> I was in fact wondering why "ofInt" rather than just "of".
> >>
> >> Best,
> >> Gilles
> >>
> >> >> [...]
>
>
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