On Mar 15, 2009, at 7:29 PM, Ronan Paixão wrote:
> Em Dom, 2009-03-15 às 17:11 -0700, kcrisman escreveu:
>>
>>> Wouldn't it be clearer if the error message read
>>>
>>> NameError: name 't' is not defined, try var('t') beforehand
>>>
>>> or something similar?
>>>
>>> Perhaps as Carl deprecates common anticipated behaviors he'd be open
>>> to having his patch adjust the permanent error messages (not just
>>> the
>>> deprecation warnings) to give advice on the correct syntax/usage
>>> when
>>> possible. I'm starting to see some of this in Ubuntu Linux and the
>>> error messages are giving hints that took me hours to discover on my
>>> own a couple years ago.
>>
>> This is an excellent idea no matter what is happening with variables,
>> assuming that this particular error message is usually the right
>> response to this NameError. That's when I see it, but I assume there
>> are other times this NameError also appears. Otherwise this sounds
>> like a ticket to open.
>>
>>> With a little python magic, we can work around this.
>>> sage: def f(x,y):
>>> ....: return x + x*y
>>> ....:
>>> sage: f.func_code.co_argcount
>>> 2
>>> sage: f.func_code.co_varnames
>>> ('x', 'y')
>>>
>>> We could write a wrapper that takes a python function, and returns
>>> another one that takes keyword arguments. Then the plotting code
>>> would
>>> use this wrapper as a preprocessor before doing anything with python
>>> functions.
>>
>> Certainly it makes sense to make this *possible*! Sure - absolutely,
>> there should be options, consistency should be possible if we can do
>> it.
>>
>> But it just seems weird to me to choose consistency as the overriding
>> factor, to the point of deprecating *unambiguous* functionality that
>> already exists and does not cause problems (e.g. plot(x^2,0,1) or
>> integrate(x^2,0,1) ).
>
> I agree. As a member of the non-math-teacher part of this list, I must
> agree that plot(some_single_var_function_or_expression, 0, 1)
> should be
> considered as valid input.
>
> I believe that as Sage wants to take over the world, it shouldn't be
> usable only by Math professionals, but also common people like me,
> which
> don't even know what is a Symbolic Ring is.
>
> OK, I concede that the docs could help with that, and that consistency
> is desirable, but that doesn't mean we should always copy Mma. Do we
> want to be better or just a clone to it? What exactly is the user
> target
> of Sage? Only math teachers doesn't count as "the whole world" for me.
>
> By the way, to be more explicit, I think the better option would be to
> allow single-variable functions or expressions to be plotted directly
> without the need (but allowing) to use variable specification in the
> range, regardless if the variable is x or anything else, provided
> there's only one.
These are my thoughts too, though I see the pros and cons. For
example, is "y + x - y" a function of one variable? Things should be
*much* tighter than the are now though.
> About the xmax, xmin, etc, I think the vmax, vmin, hmax, hmin proposed
> before could be used at least for cartesian plots, since vertical and
> horizontal directions are common for any used variable.
Personally, I would expect xmin, xmax, etc. well before I would
expect hmin, hmax... even if I'm graphing something that doesn't have
an x. Imagine graphing h(x).
- Robert
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