On 10/6/2017 8:44 AM, ROGER GRAYDON CHRISTMAN wrote:
Despite the documentation, I would still be tempted to say that range is a function.
It is, *according* to the documentation. Built-in classes are included in Library Reference, Ch. 2, Built-in Functions. Changing that to "Built-in Functions and Classes" has been proposed (perhaps by me) and rejected.
Taking duck-typing to the meta-level, every time I use range, I use its name followed by a pair of parentheses enclosing one to three parameters, and I get back an immutable sequence object. It sure looks like a function to me.
In the standard mathematical sense it is, more so than instances of classes <function> or <built-in function), such as print, that operate mainly by side effects.
I would similarly say that map is a function, or an iterator generator I write myself with yield statements is a function,
Functions with 'yield' are 'generator functions'
both of which also return sequences.
Iterators are mutable representatives of sequences, but cannot be indexed.
It is not clear to me what the difference really is between my conception and the official definition -- is it a question about whether it returns a first-class object?
No. All python callables (functions in the broad sense) return objects.
Or more simply, what is the clear and obvious distinction that I can give to my non-scientific laypeople about why range isn't a function, if it looks like one?
It is a function, in the usual sense not specific to Python, that is specifically a Python class. It is not just a function. It is a function that returns an instance of itself when called. This is the distinguishing feature of classes as functions (callables).
-- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
