Em Sex, 2008-11-21 às 16:44 -0700, dean moore escreveu: > Haven't posted anything to this list in a long time. Posting to both > lists -- unsure of proper bin. > > Searched & googled, couldn't find this previously reported or solved > -- sorry if I'm spamming. > > Running SAGE Version 3.1.2 on Ubuntu Linux in notebook, though about > same happened > command line. > > Scenario one: > > f = x**2 # Quadratic function > g = f.derivative() > print g > print g(3) > > get > 2 x > > 6 > Good & wonderful. > > Scenario two: > > f = x # Constant function > g = f.derivative() > print g > print g(3) > > get > 1 > Traceback (click to the left for traceback) > ... > > ValueError: the number of arguments must be less than or equal to 0 > 1 > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > > File "/home/dino/.sage/sage_notebook/worksheets/admin/3/code/15.py", line > 9, in <module> > print g(Integer(3)) > File > "/home/dino/Desktop/sage-3.1.2-debian-x86_64-intel-x86_64-Linux/local/lib/python2.5/site-packages/SQLAlchemy-0.4.6-py2.5.egg/", > line 1, in <module> > > > File > "/home/dino/Desktop/sage-3.1.2-debian-x86_64-intel-x86_64-Linux/local/lib/python2.5/site-packages/sage/calculus/calculus.py", > line 1671, in __call__ > raise ValueError, "the number of arguments must be less than or equal to > %s"%len(self.variables()) > > ValueError: the number of arguments must be less than or equal to 0 > > Why does SAGE dislike calling a constant function a function? >
The problem lies in that when you say f = x, you're not creating a function, but just assigning x to another variable name. The difference is subtle, but here is some example to clarify: f = x print type(f) g = f.derivative() print type(g) f(x) = x print type(f) g = f.derivative() print type(g) You get: <class 'sage.calculus.calculus.SymbolicVariable'> <class 'sage.calculus.calculus.SymbolicConstant'> <class 'sage.calculus.calculus.CallableSymbolicExpression'> <class 'sage.calculus.calculus.CallableSymbolicExpression'> Notice that when you explicitly use f(x) sage interprets that as a function. Your scenario one works because when you use x**2 you're applying an operation to a variable x and sage implicitly sees this differently. Also, you still get something different: f = x**2 print type(f) <class 'sage.calculus.calculus.SymbolicArithmetic'> But that is also callable as a function. Ronan Paixão --~--~---------~--~----~------------~-------~--~----~ 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://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
