On Wed, Nov 12, 2008 at 12:20 AM, Ondrej Certik <[EMAIL PROTECTED]> wrote:
>
> Hi Lance!
>
> On Tue, Nov 11, 2008 at 7:31 PM, llarsen <[EMAIL PROTECTED]> wrote:
>>
>> It seems like it would be nice where possible to make the sympy syntax
>> as natural as possible. One area where it seems like this could be
>
> Absolutely, thanks for giving us a feedback.
>
>> done is in substitutions. I think it would be really slick support a
>> substitution syntax like the following:
>>
>> from sympy import *
>> x,y = symbols("xy")
>> f = x**2+y**2
>>
>> # Substitute in x as 1 and y as 2
>> print f(x=1, y=2)
>>
>> Output > 5
>>
>> Currently you can do this using:
>> print f.subs({x:1,y:2})
>>
>> However, f(x=1,y=2) is a more standard mathematical notation. It seems
>> like this would be a rather trivial change. A __call__ method could be
>> added to the Basic class (to make Basic objects callable as
>> functions). The call method could just invoke the subs method directly
>> and return the result. The subs could be modified to support the
>> additional syntax:
>>
>> f.subs(x=1, y=2)
>>
>> I am interested to hear what others think, but I really like the idea
>> and think it would prove convenient.
>
> Thanks a lot for your suggestion. This is how Sage does it -- but it
> has one drawback: it only works for symbols, but not if you are
> substituting for x**2 or anything more complex. I personally see this
> as some kind of a hack, as a misusing of keywords arguments,
> but I think we can support this syntax, even though it would only work
> for symbols. I think a lot of people want this. Others, what do you
> think?
>
> Ondrej
I have often found myself wanting to type something like this, so I'm for it.
I would probably allow more things sage does, such as:
sage: f = x*y
sage: f(3,2)
6
sage: f(3)
3*y
sage: f(x,2)
2*x
sage: f(x=3)
3*y
sage: f(y=2)
2*x
>
> >
>
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