q-lang-users

[q-lang-users] Unparse on Rationals

[Rob H. <hub...@gm...>]

At the moment, unparse on (positive) Rational values always produces a 
value of the form
    N%D
(well, pending the change to (%) from (over) anyway).
Is this what is really desired?

I wondered whether it would be preferable to present, for example:

    3%1  as just  3
        The LHS has the advantage of looking like the rational it is
        The RHS is clearly simpler

    11%5  as  2+1%5
        The LHS is simpler this time
        The magnitude of the RHS more obvious (i.e. that it's "2 and a bit")

I prefer the RHS in both cases.

Comments welcome.

Thanks,
Rob.

Re: [q-lang-users] Unparse on Rationals

[John C. <co...@cc...>]

Rob Hubbard scripsit:

> I wondered whether it would be preferable to present, for example:
> 
>     3%1  as just  3
>         The LHS has the advantage of looking like the rational it is
>         The RHS is clearly simpler

I prefer the RHS here, but worry about people being misled by it.
Would you want to see 3+0*i as 3 also?

>     11%5  as  2+1%5
>         The LHS is simpler this time
>         The magnitude of the RHS more obvious (i.e. that it's "2 and a bit")

I definitely prefer the LHS in this case, because 2+1%5+3+2%5*i is
completely misleading (or would it be parenthesized by the unparser?)

-- 
John Cowan   <co...@cc...>   http://www.ccil.org/~cowan
One time I called in to the central system and started working on a big
thick 'sed' and 'awk' heavy duty data bashing script.  One of the geologists
came by, looked over my shoulder and said 'Oh, that happens to me too.
Try hanging up and phoning in again.'  --Beverly Erlebacher

Re: [q-lang-users] Unparse on Rationals

[Rob H. <hub...@gm...>]

John Cowan wrote:
> Rob Hubbard scripsit:
>
>   
>> I wondered whether it would be preferable to present, for example:
>>
>>     3%1  as just  3
>>         The LHS has the advantage of looking like the rational it is
>>         The RHS is clearly simpler
>>     
>
> I prefer the RHS here, but worry about people being misled by it.
> Would you want to see 3+0*i as 3 also?
>
>   
I suppose that's related to the normal form problem that you mentioned 
before.
Well, I'd like these to be mutually consistent: both simplified, or 
neither simplified.
>>     11%5  as  2+1%5
>>         The LHS is simpler this time
>>         The magnitude of the RHS more obvious (i.e. that it's "2 and a bit")
>>     
>
> I definitely prefer the LHS in this case, because 2+1%5+3+2%5*i is
> completely misleading (or would it be parenthesized by the unparser?)
>   
It would have to be (2+1%5)+(3+2%5)*i.
Yes, I think I prefer 11%5+17%5*i in this case too.

Rob.

Re: [q-lang-users] Unparse on Rationals

[Albert G. <Dr....@t-...>]

John Cowan wrote:
> Rob Hubbard scripsit:
> 
>>I wondered whether it would be preferable to present, for example:
>>
>>    3%1  as just  3
>>        The LHS has the advantage of looking like the rational it is
>>        The RHS is clearly simpler

No, I definitely have to oppose this. :) It should be clear to see that 
it is a rational number, so 3%1, not 3. For the same reason, a complex 
number is unparsed as X+Y*i even if Y is zero. (Currently I do simplify 
the case of a zero real part, though, in this case the number would be 
printed as just Y*i, but that also makes it clear that it's a complex 
number.)

>>    11%5  as  2+1%5
>>        The LHS is simpler this time
>>        The magnitude of the RHS more obvious (i.e. that it's "2 and a bit")
> 
> I definitely prefer the LHS in this case, because 2+1%5+3+2%5*i is
> completely misleading (or would it be parenthesized by the unparser?)

Yes the LHS, again. If you need a better format to see the magnitude, 
well that's what ratutils::str_mixed is for.

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [q-lang-users] Unparse on Rationals

[Rob H. <hub...@gm...>]

On 22/06/06, Albert Graef <Dr....@t-...> wrote:
> John Cowan wrote:
> > Rob Hubbard scripsit:
> >
> >>I wondered whether it would be preferable to present, for example:
> >>
> >>    3%1  as just  3
> >>        The LHS has the advantage of looking like the rational it is
> >>        The RHS is clearly simpler
>
> No, I definitely have to oppose this. :) It should be clear to see that
> it is a rational number, so 3%1, not 3. For the same reason, a complex
> number is unparsed as X+Y*i even if Y is zero. (Currently I do simplify
> the case of a zero real part, though, in this case the number would be
> printed as just Y*i, but that also makes it clear that it's a complex
> number.)

Thanks. That was the sort of answer I was after: definite.

I was still not certain of the intention behind unparse, i.e. whether
just the semantic value should be presented to the user as simply as
possible, or whether the type should also be indicated. Clearly it is
the latter.

> >>    11%5  as  2+1%5
> >>        The LHS is simpler this time
> >>        The magnitude of the RHS more obvious (i.e. that it's "2 and a bit")
> >
> > I definitely prefer the LHS in this case, because 2+1%5+3+2%5*i is
> > completely misleading (or would it be parenthesized by the unparser?)
>
> Yes the LHS, again. If you need a better format to see the magnitude,
> well that's what ratutils::str_mixed is for.

Okay. Similarly, thanks.

Rob.