On Mon, Sep 26, 2011 at 7:45 AM, Paul Moore <p.f.moore@gmail.com> wrote:
On 26 September 2011 12:34, Nick Coghlan <ncoghlan@gmail.com> wrote:
On Mon, Sep 26, 2011 at 2:56 AM, Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:
So, your proposed use of 'nonlocal' would actually be declaring a name to be *local*. That strikes me as weird and perverse.
Ah, but it *wouldn't* be local, that's the point - it would be stored on the function rather than on the frame, and hence be shared across invocations.
Hmm, its lifetime is non-local, but the visibility is still local. My instincts associate the word "(non-)local" with visibility rather than lifetime.
If you want a bikeshed to colour in, maybe "persistent" is a better keyword for this:
def counter(): persistent n as 1 print(n) n += 1
Adding new keywords is a big, big step that demands a compelling justification. Now that I have come up with a way to make this syntactic sugar for existing usage of nonlocal rather than a new concept, I flatly oppose introduction of a new name for something which is, at a fundamental level, just a variation on existing functionality. I'd rather continue with the status quo indefinitely if people truly find this variant intolerable. It may be easier to turn things around and specifically look at it from the "syntactic sugar" point of view: # Current syntax def _outer(): # Boilerplate VAR = EXPR def FUNC(): # Real function name is hidden nonlocal VAR # VAR repeated # Do stuff with VAR, including rebinding it return f # Boilerplate FUNC = _outer() # Boilerplate and FUNC repeated Most of that code is noise: the interesting aspects are that: 1. There is a function called FUNC() available for use 2. VAR survives across invocations of FUNC() 3. At the first invocation of FUNC(), the initial value of VAR will be EXPR So, let's offer a syntax that just includes those 3 pieces of interesting information without the boilerplate: def FUNC(): # Function of interest is not hidden in a nested scope nonlocal VAR from EXPR # Shared variable and initial value # Do stuff with VAR Is anyone going to *guess* what that means without looking it up? Probably not. But are they going to *forget* what it means once they learn it? Also probably not. "I can guess what this means without reading the docs or having someone explain it to me" is setting the bar too high for what a single keyword can possibly hope to convey. The bar needs to be whether or not it serves as a useful mnemonic to recall the functionality once a user already know what means. For me, 'nonlocal' fits that bill, especially when the feature is described as syntactic sugar for a somewhat common use case for the existing lexical scoping functionality. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia