On Dec 28, 2007 10:18 AM, Pearu Peterson <[EMAIL PROTECTED]> wrote:
>
>
> On Dec 28, 9:11 am, kent-and <[EMAIL PROTECTED]> wrote:
>
> > class Foo:
> >
> > def __init__(self):
> > self.field = 1.0
> >
> > def __mul__(self, other):
> > print "Multiplication in Foo from right"
> > self.field = self.field * other
> >
> > def __rmul__(self, other):
> > print "Multiplication in Foo from left"
> > self.field = other * self.field
> >
> > f = Foo()
> >
> > f*x # works
> > x*f # works
> >
> > f*y # works
> > y*f # does not work
> >
> > What should I do about this ?
>
> Try deriving Foo from sympy.Basic. Actually the __mul__ code in sympy
> is broken as it should return NotImplemented when it gets an
> unknown (to sympy) object as an right hand side.
It raises:
Traceback (most recent call last):
File "t.py", line 21, in ?
y*f # does not work
File "/home/ondra/sympy/sympy/core/methods.py", line 32, in __mul__
return Basic.Mul(self, other)
File "sympy/core/basic_methods.py", line 122, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "/home/ondra/sympy/sympy/core/operations.py", line 19, in __new__
c_part, nc_part, lambda_args, order_symbols =
cls.flatten(map(Basic.sympify, args))
File "sympy/core/basic.py", line 270, in sympify
raise ValueError("%r is NOT a valid SymPy expression" % a)
ValueError: '<__main__.Foo instance at 0xb7dbf14c>' is NOT a valid
SymPy expression
So maybe we could check in the mul, if a ValueError exception gets
raised in sympify and reraise
NotImplemented instead?
> Btw, arithmetic operations in sympycore are about 4x faster than
> in sympy and I am currently working on sexpr support (based on
> Fredrik's research) which should give speedups upto 10x in arithmetic
> operations.
Excellent. Now we need to port this to SymPy:
http://code.google.com/p/sympy/issues/detail?id=486
You may also be interested in some timings I did:
http://groups.google.com/group/sage-support/msg/8f1a7ed5a49df1a0
where sympycore was 3x faster than SymPy.
Ondrej
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