Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 13/08/2013 01:19, Ian P. Cooke a écrit : I'm reminded of the work done at Microsoft the showed that Observable and Enumerable were duals (e.g. http://csl.stanford.edu/~christos/pldi2010.fit/meijer.duality.pdf ) The relevant

Re: [rust-dev] Adding "else" on "for" loops, like Python

I'm reminded of the work done at Microsoft the showed that Observable and Enumerable were duals (e.g. http://csl.stanford.edu/~christos/pldi2010.fit/meijer.duality.pdf ) The relevant idea is that a richer interface that includes wether the the subject completed normally or via exception is ver

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 12/08/2013 20:16, Corey Richardson a écrit : On Mon, Aug 12, 2013 at 2:54 PM, Simon Sapin wrote: fn main() { let v = ~[1u, 7, 42, 0]; let mut it = v.move_iter().enumerate(); for_!((i, v) in it { if v == 42 { printfln!("Found it at %u", i); br

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Mon, Aug 12, 2013 at 2:54 PM, Simon Sapin wrote: > fn main() { > let v = ~[1u, 7, 42, 0]; > let mut it = v.move_iter().enumerate(); > for_!((i, v) in it { > if v == 42 { > printfln!("Found it at %u", i); > break > } > } else { > pr

Re: [rust-dev] Adding "else" on "for" loops, like Python

Given that many people have noted that they've never used it in python, and nobody seems to agree on what the intuitive behavior for it would be, and all such behaviors can be implemented via macros, I think we'll pass. -Graydon ___ Rust-dev mailing lis

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 11/08/2013 21:30, Tom Lee a écrit : On Sun, Aug 11, 2013 at 1:27 PM, Patrick Walton mailto:pwal...@mozilla.com>> wrote: On 8/12/13 8:25 AM, Tom Lee wrote: :) I can appreciate that, but I'm still not really convinced that this "problem" deserves more syntax.

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 12/08/2013 18:23, Micah Chalmer a écrit : The for-loop already knows how it exited. It only "knows" if something explicitly makes it know. This boils down to one of two things: either the boolean flag approach as discussed earlier, or the compiler turning every "break" in the block into an e

Re: [rust-dev] Adding "else" on "for" loops, like Python

> The only way to implement .finished() non destructively (so that, when > returning false, it does not eat an element) is with a Peekable iterator as > in this pull request: > > https://github.com/mozilla/rust/pull/8428 > > Then .finished() is .peek().is_none(). If you loop all the way throug

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 11/08/2013 23:18, Jens Nockert a écrit : for i in iterations { … if converged { break; } } if iterations.finished() { fail!("Oh noes, it did not converge"); } The only way to implement .finished() non destructively (so that, when returning false, it does not eat an element

Re: [rust-dev] Adding "else" on "for" loops, like Python

For reference, in my iterative proposal, I've been considering adding a `.finished()` method to the Fuse adaptor, which would let you easily add that capability to any iterator. -Kevin Ballard > On Aug 11, 2013, at 6:47 PM, Daniel Micay wrote: > >> On Sun, Aug 11, 2013 at 6:32 PM, Tom Lee wr

Re: [rust-dev] Adding "else" on "for" loops, like Python

Hi, On 12/08/2013 00:10, Daniel Micay wrote: Perhaps it's a violation of the protocol to stop raising StopIteration, but zip will continue to cause side effects like I/O. It's undefined what happens if you continue producing items after you stopped. There are no safeguards in place. However a

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Sun, Aug 11, 2013 at 6:58 PM, Armin Ronacher wrote: > Hi, > > > On 11/08/2013 23:47, Daniel Micay wrote: >> >> Python does not make the guarantee, and the functions like `zip` there >> will continue calling the underlying iterators. > > That's incorrect. Python's definition of the iterator pro

Re: [rust-dev] Adding "else" on "for" loops, like Python

Hi, On 11/08/2013 23:47, Daniel Micay wrote: Python does not make the guarantee, and the functions like `zip` there will continue calling the underlying iterators. That's incorrect. Python's definition of the iterator protocol is that an iterator not continue raising StopIteration is in violat

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Sun, Aug 11, 2013 at 6:32 PM, Tom Lee wrote: > > On Sun, Aug 11, 2013 at 3:18 PM, Jens Nockert wrote: >> >> >> On 12 Aug 2013, at 00:09, Tom Lee wrote: >> >> Anyway, this sort of confusion is exactly why I don't like for..else. But >> then maybe I'm the only one that's confused here. :) >> >>

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Sun, Aug 11, 2013 at 3:18 PM, Jens Nockert wrote: > > On 12 Aug 2013, at 00:09, Tom Lee wrote: > > Anyway, this sort of confusion is exactly why I don't like for..else. But > then maybe I'm the only one that's confused here. :) > > > Obviously you were not the only one, since there was a long

Re: [rust-dev] Adding "else" on "for" loops, like Python

On 12 Aug 2013, at 00:09, Tom Lee wrote: > Anyway, this sort of confusion is exactly why I don't like for..else. But > then maybe I'm the only one that's confused here. :) Obviously you were not the only one, since there was a long thread without clarification. While I think it is reasonably

Re: [rust-dev] Adding "else" on "for" loops, like Python

On H.25/08/11, at 22:20, Tom Lee wrote: > To be clear: should that `if` test be "if not converged" ? No, the else in Python executes if the for loop consumes the whole iterator, and you want to fail if it does not converge. ___ Rust-dev mailing list R

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Sun, Aug 11, 2013 at 1:27 PM, Patrick Walton wrote: > On 8/12/13 8:25 AM, Tom Lee wrote: > >> :) I can appreciate that, but I'm still not really convinced that this >> "problem" deserves more syntax. >> >> That said, I might hate for..else less if it used something other than >> the 'else' key

Re: [rust-dev] Adding "else" on "for" loops, like Python

On 8/12/13 8:25 AM, Tom Lee wrote: :) I can appreciate that, but I'm still not really convinced that this "problem" deserves more syntax. That said, I might hate for..else less if it used something other than the 'else' keyword. *shrug* It seems to me that a big benefit of macros in Rust is to

Re: [rust-dev] Adding "else" on "for" loops, like Python

On Sun, Aug 11, 2013 at 1:06 PM, Simon Sapin wrote: > Le 11/08/2013 06:53, Tom Lee a écrit : > > I think your code will be more explicit if you declare a mut bool & >> check its state post-`break`. :) >> > > Resorting to boolean flags to cope with insufficient control flow feels > like Basic, wh

Re: [rust-dev] Adding "else" on "for" loops, like Python

To be clear: should that `if` test be "if not converged" ? On Sun, Aug 11, 2013 at 1:18 AM, Jens Nockert wrote: > I wouldn't call myself a Python programmer, but I have written a lot of > Python and I know quite a few that do use and love the "for-else" construct. > > The most common (if not on

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 11/08/2013 06:53, Tom Lee a écrit : I think your code will be more explicit if you declare a mut bool & check its state post-`break`. :) Resorting to boolean flags to cope with insufficient control flow feels like Basic, which makes me sad :( -- Simon Sapin ___

Re: [rust-dev] Adding "else" on "for" loops, like Python

I wouldn't call myself a Python programmer, but I have written a lot of Python and I know quite a few that do use and love the "for-else" construct. The most common (if not only?) usage that I have seen is something like for i in xrange(…): some-algorithm… if coverged: break el

Re: [rust-dev] Adding "else" on "for" loops, like Python

I'm not very familiar with Python at all, coming from C++ land. At first glance, I must say that this seems totally backward and not desirable; I'd wager any case where this for...else would come in handy has an alternate design that is just as sexy (or more) and does not require the pattern. T

Re: [rust-dev] Adding "else" on "for" loops, like Python

I'm a big Python user, but I'm -1 on for..else -- mostly because of the choice of the "else" keyword. The issue is that it's downright misleading. You don't look at the 'else' clause and think "oh, I don't know what that means" & go look up the docs like you might with other unfamiliar parts of a

Re: [rust-dev] Adding "else" on "for" loops, like Python

On 08/10/2013 07:24 PM, Paul Nathan wrote: On 8/10/13 7:10 AM, Simon Sapin wrote: Hi, Now that the for loop is based on external iterators, can we reconsider "for-else"? Proposal: for i in iter { // ... } else { // ... } The optional else block is executed wh

Re: [rust-dev] Adding "else" on "for" loops, like Python

On 8/10/13 7:10 AM, Simon Sapin wrote: > Hi, > > Now that the for loop is based on external iterators, can we reconsider > "for-else"? > > Proposal: > > for i in iter { > // ... > } else { > // ... > } > > The optional else block is executed when the for loop stops w

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 10/08/2013 15:10, Simon Sapin a écrit : Proposal: for i in iter { // ... } else { // ... } The optional else block is executed when the for loop stops without exhausting the iterator, ie. when "break" is used. Typical usage is finding an element in a

Re: [rust-dev] Adding "else" on "for" loops, like Python

In all my programming career as a python programmer I have never used a for-else construct. In fact, I won't be able to tell you exactly when the else-block is executed off the top of my head either. Even though that probably speaks more about me as a programmer than about the python language, it a

Re: [rust-dev] Adding "else" on "for" loops, like Python

Le 10/08/2013 15:56, Jordi Boggiano a écrit : On 10.08.2013 16:10, Simon Sapin wrote: >Proposal: > > for i in iter { > // ... > } else { > // ... > } > >The optional else block is executed when the for loop stops without >exhausting the iterator, ie. when "break" is u

Re: [rust-dev] Adding "else" on "for" loops, like Python

On 10.08.2013 16:10, Simon Sapin wrote: > Proposal: > > for i in iter { > // ... > } else { > // ... > } > > The optional else block is executed when the for loop stops without > exhausting the iterator, ie. when "break" is used. Maybe that's common to python devs, bu

[rust-dev] Adding "else" on "for" loops, like Python

Hi, Now that the for loop is based on external iterators, can we reconsider "for-else"? Proposal: for i in iter { // ... } else { // ... } The optional else block is executed when the for loop stops without exhausting the iterator, ie. when "break" is used. --