On 11/07/11 21:03, kcrisman wrote:
>
> So are you saying that Python and Piecewise functions will no longer
> behave correctly if this behavior goes from warning to error? It
> would be great if you had a "toy" example with full code; maybe there
> is a workaround that needs to become standard practice here...
>
> - kcrisman
>
Here's an example of the warning on a python function. It's just showing
the warning in the wrong place.
I've commented the point in the function where the warning really gets
thrown, but I can't figure out a way to get rid of the warning and make
the function work at the same time.
I'm aware that my entire approach here is stupid; I'm willing to accept
any replacements that work as well or better =)
$ cat python_function_test.py
#!/home/mjo/bin/sage
from sage.all import *
def please_substitute_function(max_degree, points, expr, func1, func2):
"""
Sage can't substitute_function on an expression with (evaluated)
derivatives.
"""
for degree in range(0, max_degree+1):
for point_idx in range(0, len(points)):
var1, var2 = var('whatever1,whatever2')
deriv1 = SR(0)
if len(func1.variables()) > 0:
var1 = func1.variables()[0]
deriv1 = derivative(func1, var1, degree)
deriv2 = SR(0)
if len(func1.variables()) > 0:
var2 = func2.variables()[0]
deriv2 = derivative(func2, var2, degree)
target = SR(0)
if len(deriv1.variables()) > 0:
# Works, but throws a warning.
target = deriv1(points[point_idx])
# No error, but doesn't work.
# target = deriv1(var1=points[point_idx])
replacement = SR(0)
if len(deriv2.variables()) > 0:
# Works, but throws a warning.
replacement = deriv2(points[point_idx])
# No error, but doesn't work.
# replacement = deriv2(var2=points[point_idx])
expr = expr.substitute_expression(target == replacement)
return expr
x = SR.symbol('x', domain='real')
f = function('f', x)
p1 = f.diff(x)(x = -1)*x**2 + f(x = 1)*x**3
g = function('g', x)
p2 = please_substitute_function(1, [-1,1], p1, f, g)
print "p1:"
print p1
print ""
print "p2:"
print p2
print ""
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