On Sat, 14 Jan 2006 18:21:28 -0500, Mike Meyer wrote: > Paul Rubin <http://[EMAIL PROTECTED]> writes: >> Mike Meyer <[EMAIL PROTECTED]> writes: >>> > Whether the '==' operation conforms to your idea of what equality >>> > means is unclear. >>> Care to say what it does mean, then? >> I'd say a==b doesn't necessarily mean a and b have the same value. > > Care to say what it does mean (as opposed to what it doesn't mean), then?
Since you can overload __eq__, it means anything the programmer wants it to mean. And if there is a bug, something he doesn't mean. But ignoring pathological cases, a==b means that a and b are equal, whatever equal means in the context. Equal might mean that a and b: - are the same object; - are different objects with equal values; - are different objects with equivalent values; - have the same value when converted to a common type (which may or may not be the type of either a or b); - are "close enough" to treat as if they were the same; - represent the same abstract quantity or quality; - have the same printable representation; - or something else! But note that even if one or more of these are true, it doesn't necessarily mean that a==b will return true. "two" and "deux" both represent the same abstract quantity, but no programming language I know of will recognise them as equal. And then there is this potent source of bugs: >>> distance_in_feet = 5 >>> weight_in_milligrams = 5 >>> distance_in_feet == weight_in_milligrams True Since when is a distance comparable to a weight, let alone equal? -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
