On 04/30/2013 10:57 PM, Chris Smith wrote:
There are different ways to organize this, but here is a compact way
-- not necessarily the best. I don't know what your 'func's look like
so I am just showing the transformation of nc by multiplying or
dividing by 2:
def mul_xform(func):
def product_bases(nc):
if len(nc) == 2 or len(nc) == 1 and nc[0].is_Pow and nc[0].exp
== 2:
return Mul._from_args(nc)
assert not nc
def updater(p, func, m):
if p.is_Mul:
c, nc = p.args_cnc(split_1=False)
if nc:
nc = product_bases(nc)
if nc not in m:
m[nc] = func(nc)
c = Mul._from_args(c)
return c*m[nc]
return p
return Transform(lambda k: updater(k, func, {}), lambda w: w.is_Mul)
T2 = mul_xform(lambda x: 2*x)
Thalf = mul_xform(lambda x: x/2)
>>> var('ex ey', commutative=False)
(ex, ey)
>>> (15*ex**2 + 6*ey*ex + ex).xreplace(T2)
ex + 30*ex**2 + 12*ey*ex
>>> _.xreplace(Thalf)
ex + 15*ex**2 + 6*ey*ex
/c
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Works great! I made one change (see below) so I could generate a
separate dictionary for different functions (I have 5 different types of
multiplication to define) -
def mul_xform(func, D):
def product_bases(nc):
if len(nc) == 2 or len(nc) == 1 and nc[0].is_Pow and nc[0].exp
== 2:
return Mul._from_args(nc)
assert not nc
def updater(p, func, m):
if p.is_Mul:
c, nc = p.args_cnc(split_1=False)
if nc:
nc = product_bases(nc)
if nc not in m:
m[nc] = func(nc)
c = Mul._from_args(c)
return c*m[nc]
return p
return Transform(lambda k: updater(k, func, D), lambda w: w.is_Mul)
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