"Carl Banks" <[EMAIL PROTECTED]> writes: > An iterator is not a sequence, and it's impossible to determine > whether an iterator is "empty" in general, except by trying to get > an item from it. [...] > > IMO, this is big time wart in the language. Iterators have no > calculatable truth value; for many other types a truth value doesn't > make sense (for instance: function objects, type objects, modules, > user-defined types that don't bother with __nonzero__). Using such > objects in a boolean context is almost always an error.
It still seems like a reasonable thing for a programmer to do though, even if the language doesn't currently support it. Would it make sense to *define* a truth value for iterators? Or at least to enable those that *are* able to say "I'm empty" to do so in a way that boolean contexts can interpret as "false"? Perhaps allowing (but not requiring) an iterator object to grow a 'len' method is the simplest way. -- \ "I like my dental hygenist, I think she's very pretty; so when | `\ I go to have my teeth cleaned, while I'm in the waiting room I | _o__) eat an entire box of cookies." -- Steven Wright | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
