Wow, thanks! I'll make up a patch right now.
On Mon, Jul 14, 2008 at 3:25 PM, cgb <[EMAIL PROTECTED]> wrote: > > I think the solution is just to define __rmul__ : > > sage: x = PolynomialRing(QQ,'x').gen() > sage: f = Piecewise([[(0,1),1*x^0]]) > sage: r = f*2 > sage: r = 2*f > --------------------------------------------------------------------------- > TypeError Traceback (most recent call > last) > /Users/boncelet/<ipython console> in <module>() > /Users/boncelet/element.pyx in > sage.structure.element.RingElement.__mul__ (sage/structure/element.c: > 8545)() > /Users/boncelet/coerce.pyx in > sage.structure.coerce.CoercionModel_cache_maps.bin_op_c (sage/ > structure/coerce.c:5338)() > TypeError: unsupported operand parent(s) for '*': 'Integer Ring' and > '<type 'instance'>' > > sage: f.__rmul__ = f.__mul__ > sage: r = f*2 > sage: r = 2*f > sage: r > Piecewise defined function with 1 parts, [[(0, 1), 2]] > > Hope this helps, > > --CGB > > > > On Jul 12, 4:17 am, "David Joyner" <[EMAIL PROTECTED]> wrote: >> Possibly, this is not a bug in Ring. For the class of Piecewise functions, >> __mul__ is implemented in a way that allows you to multiply >> two elements in that class. If you try to multiply a piecewise times a >> rational >> (in that order) then it detects this and creats on the fly a piecewise >> function >> equal to the rational on the range of the first function, then multiplies >> them. >> However, if you multiply a rational c times a piecewise f (in that order), >> then Python applies __mul__ from QQ and tries to carry out the >> multiplication. >> When writing piecewise.py, could not figure out how to implement that. >> >> sage: x = PolynomialRing(QQ, 'x').gen() >> sage: f = Piecewise([[(0,1),1*x^0]]) >> sage: r = f*2 >> sage: P1 = f.plot() >> sage: P2 = r.plot() >> sage: show(P1+P2) >> sage: two = Piecewise([[(0,1),2*x^0]]) >> sage: f*two >> Piecewise defined function with 1 parts, [[(0, 1), 2]] >> sage: two*f >> Piecewise defined function with 1 parts, [[(0, 1), 2]] >> sage: f*two == f*2 >> True >> >> Worst, if a piecewise is defined using lambda functions then >> either 2*f nor f*2 works! >> >> sage: one = lambda x:1 >> sage: f = Piecewise([[(0,1),one]]) >> sage: f*2 >> --------------------------------------------------------------------------- >> TypeError Traceback (most recent call last) >> >> /home/wdj/sagefiles/sage-3.0.4.rc0/<ipython console> in <module>() >> >> /home/wdj/sagefiles/sage-3.0.4.rc0/local/lib/python2.5/site-packages/sage/f >> unctions/piecewise.py >> in __mul__(self, other) >> 1403 for j in range(N-1): >> 1404 x0 = endpts[j+1] >> -> 1405 >> fcn.append([(endpts[j],endpts[j+1]),R(other)*self.which_function(x0)]) >> 1406 return Piecewise(fcn) >> 1407 self_endpts = self.end_points() ## we assume these start >> >> /home/wdj/sagefiles/sage-3.0.4.rc0/element.pyx in >> sage.structure.element.RingElement.__mul__ >> (sage/structure/element.c:8814)() >> >> /home/wdj/sagefiles/sage-3.0.4.rc0/coerce.pyx in >> sage.structure.coerce.CoercionModel_cache_maps.bin_op_c >> (sage/structure/coerce.c:5582)() >> >> TypeError: unsupported operand parent(s) for '*': 'Univariate >> Polynomial Ring in x over Rational Field' and '<type 'function'>' >> >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> >> On Fri, Jul 11, 2008 at 9:55 PM, cgb <[EMAIL PROTECTED]> wrote: >> >> > Hi, I'm brand new to sage, just installed it on my mac, and was going >> > through some of the examples and found a bug when I tried to multiply >> > a piecewise function by a constant: >> >> > sage: x = PolynomialRing(QQ, 'x').gen() >> > sage: f = Piecewise([[(0,1),1*x^0]]) >> > sage: r = f*2 >> > sage: r = 2*f >> > --------------------------------------------------------------------------- >> > TypeError Traceback (most recent call >> > last) >> >> > /Users/boncelet/<ipython console> in <module>() >> >> > /Users/boncelet/element.pyx in >> > sage.structure.element.RingElement.__mul__ (sage/structure/element.c: >> > 8545)() >> >> > /Users/boncelet/coerce.pyx in >> > sage.structure.coerce.CoercionModel_cache_maps.bin_op_c (sage/ >> > structure/coerce.c:5338)() >> >> > TypeError: unsupported operand parent(s) for '*': 'Integer Ring' and >> > '<type 'instance'>' >> > -------- >> >> > Multiplication should be communicative. I suspect the .__mul__ method >> > is set incorrectly. (If memory serves, python can have separate >> > methods for left and right multiplication.) >> >> > ---CGB > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
