On 04/14/2017 02:10 PM, oldk1331 wrote:
> There are 8 rational/rational?/rationalIfCan, all
> of them are defined under
> "if R has IntegerNumberSystem then ..."
>
> And seems these functions are not used in other places.
>
> They are basicly wrappers over
> retractIfCan : % -> Union(Integer, "failed")
> which is from IntegerNumberSystem.
>
> So I think they are not useful and can be removed.
> Opinions?
Erm, do you think that
rational: Octonion(R) -> Fraction(Integer)
is not useful?
Maybe it is not used in the library, but I wouldn't call it "not useful".
Same for the meaning of rational in OrderedCompletion(R),
OnePointCompletion(R), Factored(R), QuaternionCategory(R), and
ComplexCategory(R).
Bronstein even introduced
)abbrev package RATRET RationalRetractions
++ Author: Manuel Bronstein
++ Description: rational number testing and retraction functions.
++ Date Created: March 1990
RationalRetractions(S : RetractableTo(Fraction Integer)) : with
rational : S -> Fraction Integer
++ rational(x) returns x as a rational number;
++ error if x is not a rational number;
rational? : S -> Boolean
++ rational?(x) returns true if x is a rational number,
++ false otherwise;
rationalIfCan : S -> Union(Fraction Integer, "failed")
++ rationalIfCan(x) returns x as a rational number,
++ "failed" if x is not a rational number;
== add
rational s == retract s
rational? s == retractIfCan(s) case Fraction(Integer)
rationalIfCan s == retractIfCan s
He must have had a good reason to do so. Maybe it's still unused, but I
don't see a good reason to remove it.
Ralf
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