Yes Vincent, that sounds much better,
Cheers,
Nishan
On Saturday, 4 October 2014 05:21:15 UTC-4, vdelecroix wrote:
>
> Hello,
>
> Is it better worded as follows?
>
> The issue: plot(h(x), 0, 4) plots the line y=x−2, not the multi-line
> function defined by h. The reason? In the command plot(h(x), 0, 4),
> first h(x) is evaluated: this means plugging the symbolic variable x
> into the function h. The inequality "x < 2" evaluates to ``False`` and
> hence ``h(x)`` evaluates to ``x - 2`` as it can be seen with
> {{{
> sage: bool(x < 2)
> False
> sage: h(x)
> x - 2
> }}}
>
> I also find misleading to have a Python argument (the x in "def
> h(x):") and a symbolic variable (here "x") having the same name. At
> least it should be mentioned.
>
> Vincent
>
> 2014-10-02 20:32 UTC+02:00, NahsiN <[email protected] <javascript:>>:
> > @slelievre I was just pointing out what I think is a typo.
> > @slelievre You are right, the clause after the statement clarifies the
> > situation. "When a symbolic equation is evaluated, as in the definition
> of
> > h,
> > if it is not obviously true, then it returns False. Thus h(x) evaluates
> to
> > x-2, and this is the function that gets plotted" But I still feel the
> whole
> >
> > thing can be worded slightly better and more concisely. The if clause is
> > evaluated anyway when one calls h(x) so there is no point in saying "x<2
> is
> > evaluated".
> > On Thursday, 2 October 2014 13:42:25 UTC-4, slelievre wrote:
> >>
> >>
> >>
> >> Le mercredi 1 octobre 2014 22:06:50 UTC+2, NahsiN a écrit :
> >>>
> >>> Hello, I don't know where to post this so redirect me as needed. I
> >>> believe I have found a typo in the sage tutorial. Under Sage Tutorial
> >>> v6.3
> >>> >> A Guided Tour >> Some Common Issues with Functions we have the
> lines
> >>> def h(x):
> >>> if x<2:
> >>> return 0
> >>> else:
> >>> return x-2
> >>>
> >>> The issue: plot(h(x), 0, 4) plots the line y=x−2, not the multi-line
> >>> function defined by h. The reason? In the command plot(h(x),0, 4),
> first
> >>>
> >>> h(x) is evaluated: this means plugging x into the function h, *which
> >>> means that **x<2** is evaluated*.
> >>>
> >>> I think the else clause is evaluated and not the if x<2 clause.
> >>> Thanks,
> >>> Nishan
> >>>
> >>
> >> You can work around this as follows:
> >>
> >> plot(lambda x: h(x), 0, 4)
> >>
> >>
> >
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