Hi, 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.
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. 2) we have the least amount of classes in there For details, see: http://code.google.com/p/sympy/issues/detail?id=329 However, there are some longterm questions: 1) when you type sin(x), it's an instance of the class "sin". Now, all classes in Python should be CamelCase, so we should rather use "Sin(x)". Currently, SymPy/SAGE/Maple uses "sin(x)", while Mathematica uses "Sin[x]". What is your opinion about this? See also: http://code.google.com/p/sympy/issues/detail?id=329#c11 I'd very much like to obey Python conventions, because this is what people expect when seeing the code for the first time. Of course we can do something like sin=Sin so that people can use both. But I am against it, since there should be just one way of doing things. And especially, there should be just one way how things are done both inside and outside SymPy, i.e. there shouldn't be one way how to create functions in SymPy core and another way how users will create functions. So for the time being, we use lower case name of some classes in SymPy, like "sin", "cos", so that we don't break the current code. 2) I was looking at how this is done in SAGE.calculus: There is: class Function_sin(PrimitiveFunction): .... sin = Function_sin() _syms['sin'] = sin example: sage: from sage.calculus.calculus import Function_sin sage: sin(x) sin(x) sage: Function_sin()(x) sin(x) sage: type(sin) <class 'sage.calculus.calculus.Function_sin'> sage: type(sin(x)) <class 'sage.calculus.calculus.SymbolicComposition'> So first there are two ways how to create a sin(x): "sin(x)", or "Function_sin()(x)" and second everything is an instance of SymbolicComposition. Currently in SymPy it's very similar, there is Sin and ApplySin, Cos and ApplyCos (in sage you just use SymbolicComposition for all those ApplySin, ApplyCos,...). In SymPy, it's a mess and we are changing that. How do you test, if "e" is of type sin? In SymPy, we would like to do this: e = sin(x) print isinstance(e, sin) (currently on needs to do isinstance(e, ApplySin), but this is going to be changed) In SymPy, we are just going to try a very simple approach and see how it goes, see the 329 issue above for details. 2) What is your position on this: sage: (sin(x)).taylor(x, 0, 5) x - x^3/6 + x^5/120 sage: taylor(sin(x), x, 0, 5) x - x^3/6 + x^5/120 shouldn't there be just one way how to do series expansion? In SymPy we also have those 2 ways - but it's kind of inconsistent, we have it for some methods, but not all. My own opinion is more in favor of removing all those module level functions (like taylor, expand), if there is a corresponding method. But there are other opinions as well. Thanks, Ondrej --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
