On Thu, 1 Jul 2010 13:40:03 -0700 (PDT)
jeral <[email protected]> wrote:
> Hi, All.
>
> Is there any way in sage to match not only given expression against
> pattern, but equivalent expressions too?
> Say, i want to match expression with pattern pat = c*x^p*y^q*z^r,
>
> (2*x^2*y^3*z^4).match(pat)
>
> works fine, but
> (x*y).match(pat)
> returns None, while x*y is special case of c*x^p*y^q*z^r.
> Maybe there is a way to match such expressions other, than to write
> additional patterns by hand?
No, we don't support this style of pattern matching.
Here is an alternative method to detect power products:
def is_power_product(ex):
"""
EXAMPLES::
sage: var('x,y,z')
(x, y, z)
sage: is_power_product(x)
True
sage: is_power_product(x*y^2)
True
sage: is_power_product(2*x*y^2)
True
sage: is_power_product(2*pi*x*y^2)
True
sage: is_power_product(sin(x))
False
sage: is_power_product(x+y)
False
"""
def test_power(t):
op = t.operator()
return op is None or op is operator.pow
op = ex.operator()
return op is None or op is operator.pow or \
(op is operator.mul and all(test_power(t) for t in
ex.operands()))
Cheers,
Burcin
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