On Wed, Jul 18, 2012 at 12:13 PM, Aaron Meurer <[email protected]> wrote: > In my branch where I'm fixing expand, I've moved the base _eval_expand > functions to Expr. The result is that for expand to work on an > object, it must be rebuildable via obj.func(*obj.args). > > There are two classes in the quantum module that came up where this > doesn't work. One is OracleGate, which is built like OracleGate(2, > lambda qubits: qubits == IntQubit(2)), which produces the .args ((0, > 1), lambda qubits: qubits == IntQubit(2)) (in general, the first > argument n is converted to range(n)). The second is WGate, which > works like WGate(3), which produces the .args (2, 1, 0) (in general, > an argument n produces reversed(range(n))). > > I was able to change OracleGate to accept its args without ambiguity. > If the first argument is an integer, it does what it does now. If > it's a tuple, succeed if it's of the form of range(N) for some N. > > WGate cannot be fixed like this, though, because there is ambiguity > for WGate(0), which can be construed as either WGate(1) or WGate() > (range(1) or range(0)). > > Since I know very little about quantum computing and Grover's > algorithm, I'd like to know what the best way to fix this is. The > options are see are: > > - Make WGate(0) be construed as range(1). Currently WGate(0) doesn't > work, which leads me to believe that you can't have a gate with 0 > quibits. This would not require breaking the current API, but might > be confusing (?).
You need to have at least 1 qubit for it to make sense. WGate(0) should really raise a ValueError. > - Break the API. Since any kind of break would be equally disruptive, > I would suggest moving to just storing n in .args, and constructing > reversed(range(n)) on the fly when it's needed. Alternately, we could > store (reversed(range(n)),), which would make it similar to > OracleGate. Yes, let's to that. Just make a property that returns reversed(range(n)) and use that when needed. Does this answer your questions? Cheers, Brian > Aaron Meurer -- Brian E. Granger Cal Poly State University, San Luis Obispo [email protected] and [email protected] -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
