> On 19 Mar 2016, at 22:49, Charles Constant via swift-evolution
> <[email protected]> wrote:
>
> I'd like to see a comparison, but Python "for" loops seem more flexible to me
> than Swifts. It's been a couple years since I moved to Swift, but I vaguely
> remember a lot of cool loop stuff in Python, like "for {} else" for empty
> loops, etc.
Python does have a few nice features, but then that’s an argument for adding
the ones we like to Swift I think. That said, the else branch for loops that
don’t run is the one that stands out to me; it seems vaguely familiar like it
might have been discussed already, but I don’t know what happened with it.
Otherwise a lot of Python’s list handling is from how values are generated,
which is what we already have Generators/Sequences so we can generate values
however we like, though it might mean defining a new type to do it. (or push
for the stdlib to add one if it’s useful enough).
Oh actually, there is one other neat feature in Python loops which is the
ability to yield; essentially it just lets you resume a loop type operation
where you left off, which can make methods simpler, as an example on the Python
wiki here: https://wiki.python.org/moin/ForLoop
<https://wiki.python.org/moin/ForLoop>
def my_range(start, end, step):
while start <= end:
yield start
start += step
for x in my_range(1, 10, 0.5):
print x
Here a function is defined to implementing a strided range, and it uses the
yield command to avoid having to add extra conditionals (not sure what that
actually compiles into, but I imagine it’s just hiding boilerplate you’d
otherwise have to add yourself), so that’s something that might be nice too.
It’s a bit of a tangent, but at the same time it is a feature that avoids some
tricky cases in Swift loops such as when you decide to break a loop but want to
resume it later; both it and else blocks on loops can avoid some common
boiler-plate, but they don’t necessarily do anything specifically that we can’t
do. There’s also a short-hand for striding through arrays if I remember right,
something like foo[:2], I don’t remember exactly, it’s been a while since I
used it, but of course that’d be ambiguous with dictionaries, but other than
brevity (which is arguably added learning curve) it’s no different than a
.stride(2) method or whatever._______________________________________________
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