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 <nishan.singh.m...@gmail.com>:
> @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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