On Jun 17, 5:34 pm, William Stein <wst...@gmail.com> wrote:
> 2009/6/17 Robert Bradshaw <rober...@math.washington.edu>:
>
>
>
> > On Jun 17, 2009, at 4:05 AM, John Cremona wrote:
>
> >> I think is is easier, both on the eye and for a beginner to
> >> understand:
>
> >> sage: x = polygen(ZZ)
> >> sage: f = 2*x**2 - x
> >> sage: f.factor()
> >> x * (2*x - 1)
>
> > Perhaps. I like the R[var] notation because it's a direct translation
> > of the mathematical notation.
>
> I love the R[var] notation too. I remember making it up and being very
> pleased.
Sure. However you cannot do R=ZZ[t] but must do R=ZZ['t'], and then
do something else to get the variable t to be assigned to the variable
which prints as 't'. that means either R.<t>=ZZ['t'] (which to a
mathematician looks like double definition), or t = ZZ['t'].gen(0)
which looks rather less mathematical (and does not end up giving the
ring a name).
Why can't these computers just know what we mean!
>
> > Note the default variable name:
>
> > sage: t = polygen(ZZ)
> > sage: t
> > x
>
> yes, that's good to point out. To make it t:
>
> sage: t = polygen(ZZ,'t')
> sage: t
> t
>
Ahah! I think I have only ever used x, so I had not noticed that....
John Cremona
> William
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