On Thu, Jun 27, 2019 at 1:41 AM Anders Hovmöller <bo...@killingar.net> wrote:
>
> On 26 Jun 2019, at 16:46, Chris Angelico <ros...@gmail.com> wrote:
> > There are many things that can be implemented with dunders, yes, but
> > in Python, I would expect these two functions to behave identically:
> >
> > def f1(x):
> > return frob(x).spam
> >
> > def f2(x):
> > f = frob(x)
> > s = f.spam
> > return s
> >
> > This correlation is critical to sane refactoring. You should be able
> > to transform f1 into f2, and then insert print calls to see what 'f'
> > and 's' are, without affecting the behaviour of the function. The
> > proposed magic would change and completely break this; and as such, it
> > violates programmer expectations *across many languages* regarding
> > refactoring.
>
> I'm out of the game for many years but isn't that potentially extremely
> different in C++ for example?
In C++, there's awkwardnesses with simply returning a struct, so I'm
going to tweak it so it returns a pointer instead (which is more
equivalent to what Python does; also, it avoids questions of whether
the object still exists - not an issue in Python because it's garbage
collected).
int f1(const char *x) {
return frob(x)->spam();
}
int f2(const char *x) {
status *f = frob(x);
int s = f->spam();
return s;
}
I don't think you can define what "f->spam" means, so I turned that
into an actual method call, too. In any case, the refactoring is still
valid, and the disassembly of these two functions will probably be
identical (since C++ compilers are allowed to optimize out local
variables).
Point is, breaking a single expression into multiple sub-expressions
is a standard action [1] when refactoring, and it should always be
safe. Any time it isn't, you probably have either an awful language or
an awful codebase. And you should post something to TheDailyWTF.
ChrisA
[1] meaning you can do one of them each round of combat, and still
have enough time for a move action
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/EBARLGWZGNUT2RNUWT7DELO4PDEGIAWI/
Code of Conduct: http://python.org/psf/codeofconduct/
