missing 'xor' Boolean operator

[Terry Reedy]

Tim Golden wrote:

> I was pondering on this yesterday, and the only case I've
> come across in my code -- and it's reasonably common --
> is checking that one and only one of two params has been
> passed. I have code which wants, say, an id or a name
> but doesn't want both. It's hardly difficult to write the
> check even now, but an built-in xor would make it fractionally
> cleaner.

I think I would just have one parameter id_name or identifier so no 
check is needed. This is a common idiom in Python where names are not 
typed. Example: param 'source' is a string (with a file name to be 
opened) or an already opened file. If you want two local vars inside the 
function, that should be kept private to the function.

tjr