I think it will be cleaner to make it a class, even with the little
you are doing. Note that if you just want something to return some
expression (i.e., eval() would always return something), you could
just use a Python function.
By the way, Lambda really shouldn't even be in consideration. If you
are naming something, that's a sign that you shouldn't use Lambda.
It's similar with Python's lambda. You would never do
mul = lambda x, y: x*y
instead of
def mul(x, y):
return x*y
Aaron Meurer
On Sun, Jun 12, 2011 at 4:21 PM, Tomo Lazovich <[email protected]> wrote:
> I think Wavefunction applies more to the latter case, where there's a known
> function that we want to return. I sort of saw it as more of a convenience
> than anything else. For one, returning the expression itself, like
> sin(n*pi*x/L), means that if you want to actually evaluate it at a point you
> have to use subs() (which I guess is not too bad, but its a little less
> intuitive than simply getting the function and being able to call psi(2)).
> It also can provide some basic helper functions for calculating
> probabilities (f*conjugate(f)) or normalization constants. The final reason
> I had is that it ended up making DifferentialOperator quite simple...as
> simple as defining an _apply_operator_Wavefunction function (though I guess
> it's just as simple to write _apply_operator_Function or
> _apply_operator_Lambda). I can go either way on this.
>
> Tomo
>
> On Sun, Jun 12, 2011 at 4:29 PM, Brian Granger <[email protected]> wrote:
>>
>> I am -1 on having a Wavefunction class. The reason is that a
>> wavefunction is just a plain old function. There is no additional
>> logic needed over a regular function. But I want to understand what
>> you are using these functions for. I can think of two types of
>> functions needed in quantum:
>>
>> * An undefined function for use in representing an unknown or abstract
>> state: <x|psi> => psi(x). For this I would just use
>> Function('psi')('x'). The name of the state (psi) can just be used
>> for the name of the function.
>> * A function for a known quantum state like the particle in a box.
>> For this case, we should just return the special function, such as
>> sin(n*pi*x/L), etc.
>>
>> Can you clarify how the functions you are using relate to these two cases?
>>
>> Cheers,
>>
>> Brian
>>
>> On Sat, Jun 11, 2011 at 2:56 PM, Tomo Lazovich <[email protected]>
>> wrote:
>> > Lambda seems to work for me except for one thing.
>> >
>> > I have a class Wavefunction for representations of states in continuous
>> > bases. It subclasses Lambda and provides some additional convenience
>> > functions. One thing it would like to do internally is calculate
>> > self.expr*conjugate(self.expr). I've found, however, that because the
>> > Lambda
>> > uses dummy variables internally, even if I initialize the function with
>> > a
>> > symbol set to real=True, that doesn't carry over to the internal
>> > expression
>> > and so the conjugate isn't very well simplified. Is there a way to get
>> > around this?
>> >
>> > Thanks!
>> >
>> > On Fri, Jun 10, 2011 at 9:19 PM, Aaron Meurer <[email protected]>
>> > wrote:
>> >>
>> >> If you just want a placeholder to keep args, use UndefinedFunction.
>> >> If you want it to have any more advanced functionality at all, create
>> >> a subclass of Function. I admit I don't know anything at all about
>> >> what you are doing, but it's very likely that the case is the latter.
>> >>
>> >> Aaron Meurer
>> >>
>> >> On Fri, Jun 10, 2011 at 5:08 PM, Vinzent Steinberg
>> >> <[email protected]> wrote:
>> >> > On 10 Jun., 02:08, Brian Granger <[email protected]> wrote:
>> >> >> Definitely use the existing Function stuff in sympy. I am not sure
>> >> >> you will even have to subclass to do this.
>> >> >
>> >> > There is also UndefinedFunction (BTW, I think we should rename it to
>> >> > AbstractFunction or similar) if you want a rather abstract function.
>> >> > If you want to implement something like sin, you should probably use
>> >> > Function.
>> >> >
>> >> > Vinzent
>> >> >
>> >> > --
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>> >> >
>> >>
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>> >
>> >
>> >
>> > --
>> > Tomo Lazovich
>> > Harvard College '11
>> > 278 Winthrop House Mail Center
>> > Cambridge, MA 02138
>> >
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>>
>>
>>
>> --
>> Brian E. Granger
>> Cal Poly State University, San Luis Obispo
>> [email protected] and [email protected]
>>
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>
>
>
> --
> Tomo Lazovich
> Harvard College '11
> 278 Winthrop House Mail Center
> Cambridge, MA 02138
>
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