On Sep 12, 1:30 pm, Robert Bradshaw <[EMAIL PROTECTED]>
wrote:
> On Sep 12, 2007, at 1:06 PM, William Stein wrote:
> >>> I have a few design questions that I would like to discuss and they
> >>> are relevant to both SymPy and SAGE, so I am posting to both
> >>> mailinglists.
>
> > Thanks. I want to preface my comments below by remarking that the
> > design constraints in SAGE and SymPy are different so the best answers
> > in each case may be different.
>
> >>> We are currently redesigning the class hierarchy in SymPy so that:
> >>> 1)
> >>> Add(sin, cos)
> >>> and
> >>> Add(sin(1),cos(1))
>
> >>> are valid constructions. Here (Add(sin, cos))(1) will produce
> >>> Add(sin(1), cos(1)). So that we can use both applied (sin(x)) and
> >>> unapplied (sin) functions.
>
> > In SAGE the following happens. Maybe this is a design mistake in
> > SAGE:
>
> > sage: f = sin + cos; f
> > sin + cos
> > sage: f(1)
> > sin + cos # design mistake? should it be sin(1) + cos(1)?
> > sage: sin(1)
> > sin(1)
>
> > It definitely seems wrong from one point of view. What's happening
> > above is that f(1) does substitution on the variables in f, of which
> > there are none. In contrast sin(1) evaluates the function sin at 1.
>
> > If somebody agrees that the above should be considered a bug
> > in SAGE, it should be added to trac.
>
> Seehttp://www.sagemath.org:9002/sage_trac/ticket/644
Is this really a good thing? It seems like it might get a little
confusing, especially when you get into some more complicated cases.
Assume that sin and cos are 1-argument functions, and pow and atan2
are 2-argument functions. What do the following mean?
(sin+cos)(1)
(sin+1)(1)
(pow+atan2)(1, 2)
(sin+cos)(1, 2)
(pow+atan2)(1)
(pow+sin)(1)
(pow+sin)(1, 2)
(pow+sin+1)(1)
Carl
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