Hi Jason,
On Tue, 17 Nov 2009 22:46:40 -0600
Jason Grout <jason-s...@creativetrax.com> wrote:
<snip>
> So I did the following, which seemed to work, but also seemed a bit
> kludgy:
>
> from functools import wraps
> def eval_if_numeric(f):
> @wraps(f)
> def my_f(*args,**kwds):
> try:
> all(CC(a) for a in args)
> except TypeError:
> return None
> return f(*args,**kwds)
> return my_f
>
> @eval_if_numeric
> def eval_f(x,t,**kwds):
> if x<=0:
> return 0
> else:
> return sin(x+t)/x
>
> f=function('f', nargs=2,eval_func=eval_f)
> plot(f(t,t),(t,-10,10))
After applying #7490, you can achieve the same with this:
def eval_f(self, x, t):
try:
return self._evalf_(RR(x), RR(t), RR)
except TypeError:
return None
def evalf_f(self, x, t, parent=None):
if x<0:
return 0
else:
return parent(sin(x+t)/x)
g = function('g', nargs=2, eval_func=eval_f, evalf_func=evalf_f)
> Also, I just discovered that the following does work:
>
> def eval_f(x,t,*args,**kwds):
> if x<0:
> return 0
> else:
> return n(sin(x+t)/x)
>
> f=function('f', nargs=2,evalf_func=eval_f)
>
> plot(f(t,t),(t,-10,10))
>
> but then f(1,1) just returns f(1,1), not sin(2).
>
> What if we made it so that there was (yet another?) eval function
> that guaranteed that inputs would not be symbolic expressions, but
> numbers---basically what my decorator above was doing. Using this
> idea, then:
>
> def eval_f(x,t,*args,**kwds):
> if x<0:
> return 0
> else:
> return sin(x+t)/x
>
> f=function('f', nargs=2,eval_num_func=eval_f)
>
> would have the following properties:
>
> sage: f(x,1)
> f(x,1)
> sage: f(1,1)
> sin(2)
> sage: f(-1,t)
> f(-1,t)
> sage: f(-1,1)
> 0
The default behavior for symbolic functions is to keep things
unevaluated if the input is exact. Making this consistent is #1158 and
#4102 on trac.
We can add an option evaluate_numeric to the function_factory()
constructor to change this default.
> 3. The documentation to "function" is horribly out of date, at least
> regarding the parameters you bring up in the example above. (Yes, I
> know, submit a patch...I'm just bringing it up...)
I added a brief description of the customizable methods to the
docstring you get with function? with the patch #7491.
Thanks.
Burcin
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