Might there be a way to do something that doesn't conflict with the
builtin max function in the same way as the (nearly reviewed) #3587
seems to avoid conflict with the builtin sum function? This would be
pretty useful, as currently:
sage: var('x,y')
(x, y)
sage: max(x,y)
x
sage: f(x)=1+x;g(x)=2-x
sage: max(f,g)
x |--> x + 1
which last result is... debatable.
- kcrisman
On Sep 16, 10:34 am, Burcin Erocal <[email protected]> wrote:
> Hi Matt,
>
> On Mon, 14 Sep 2009 05:02:54 -0700 (PDT)
>
> Matt Rissler <[email protected]> wrote:
> > Is it possible to have max behave as you would expect with a symbolic
> > expression, i.e. wait until you evaluate it or restrict the domain to
> > check what is the maximum of the two or more values.
>
> Below is a quick implementation of a symbolic max function. It seems
> to work here:
>
> sage: max_symbolic = MaxSymbolic()
> sage: max_symbolic(5,0)
> 5
> sage: max_symbolic(x,0)
> max(x, 0)
> sage: max_symbolic(x,0).subs(x=5)
> 5
>
> Is this at all useful? Note that trying to evaluate this many times
> might be very very slow.
>
> Cheers,
> Burcin
>
> ----
>
> from sage.symbolic.function import SFunction
>
> class MaxSymbolic(SFunction):
> def __init__(self):
> SFunction.__init__(self, 'max', eval_func=self._eval_)
>
> def _eval_(*args):
> largs = len(args)
> if largs == 0:
> raise TypeError, "expected one or more arguments"
> if largs == 1:
> return args[0]
>
> res = 0
> for x in args:
> try:
> if hasattr(x, 'pyobject'):
> pyobj = x.pyobject()
> else:
> pyobj = x
> except TypeError:
> return None
> res = max(pyobj, res)
>
> return res
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