Re-write closures chapter #23568

steveklabnik · 2015-03-20T21:36:06Z

glaebhoerl · 2015-03-20T22:00:11Z

src/doc/trpl/closures.md

-the name: a closure "closes over its environment." What does that mean? It means
-this:
+```rust
+let plus_one = |x: i32| -> i32 x + 1;


Per rust-lang/rfcs#968 braces will be required here.

mdinger · 2015-03-21T23:47:25Z

On the whole, I think this is very informative. It's use of Box, traits, and various dispatch types seems to reinforce the idea that in Rust, there are a few important ideas which extend to be very encompassing and cohesive. It's not just a disparate set of parts cobbled together in odd ways. Some parts of the language probably feel more this way than others.

Little was said about the differences between Fn, FnMut, FnOnce. That's the only other thought I had.

nikomatsakis · 2015-03-23T19:59:08Z

src/doc/trpl/closures.md


-println!("The sum of 5 plus 1 is {}.", add_one(5));
+```rust
+let plus_one = |x| x + 1;


one warning: I expect that the fix for #23319 will cause this not to work unless you annotate the type of x (|x: i32|)

makes sense. let's see which one lands first, I guess.

well, it's still working

steveklabnik · 2015-03-24T15:56:59Z

Added some commits to address some of the additional stuff. I think I'll wait till #23282 to land before I polish the rest off, since that changes some things.

Manishearth · 2015-03-28T08:00:05Z

(#23282 landed)

reem · 2015-03-28T22:19:43Z

src/doc/trpl/closures.md

-interesting, but when you combine them with functions that take closures as
-arguments, really powerful things are possible.
+Rust not only has named functions, but anonymous functions as well. Anonymous
+functions that have an associated environment are called 'closures', and Rust


There's a comma splice in this sentence - how about:

Anonymous functions which have an associated environment are called 'closures' since they 'close' over their environment. Rust has a flexible implementation of closures that centers around overloading the calling operator: ().

You might want to drop the bit about (), but I just wanted to say something else in that sentence other than "the rust version is cool."

introductions are hard. I re-worded this slightly, but don't know what exactly to add. I'm not sure describing it as () overloading really captures what I love about closures.

reem · 2015-03-28T23:18:57Z

src/doc/trpl/closures.md

-the enclosing stack frame. Moving closures are most useful with Rust's
-concurrency features, and so we'll just leave it at this for
-now. We'll talk about them more in the "Concurrency" chapter of the book.
+# Closure implementation


This section comes far too late in my opinion. If you don't know about these traits, it significantly hampers your ability to form a clear mental model while reading the beginning of this guide.

You show use, then you show implementation.

steveklabnik · 2015-03-31T03:40:56Z

Okay, updated to address feedback.

@nikomatsakis , with the new subtyping relationship, how do I specify the associated type? The 'this is what Rust expands your code to' section is incorrect, but I'm not sure how to make it right.

nikomatsakis · 2015-03-31T09:00:42Z

@steveklabnik let's touch base on this!

nikomatsakis · 2015-04-01T09:21:49Z

src/doc/trpl/closures.md

+
+You'll notice a few things about closures that are a bit different than regular
+functions defined with `fn`. The first of which is that we did not need to
+annotate the types of arguments the closure takes or the values it returns. We


One problem is that, in your example, you did need to annotate the type of the argument (but not the return). This is ... frequently but not always necessary if there is no expected type (that is, if the || expression does not appear in a context that implies the type of the arguments, such as foo(|| ..)).

The problem of course is that to include a caller, you must explain that part, which I know you're trying to avoid. Maybe just a note saying something like "you can elide the argument types too, when the closure is used as part of a call expression. we'll see that later."

i've tweaked some things, this shoudl be good now

richo · 2015-04-01T18:31:40Z

src/doc/trpl/closures.md

+```rust
+fn  plus_1 (  x: i32 ) -> i32 { x + 1 }
+let plus_2 = |x: i32 | -> i32 { x + 1 };
+let plus_3 = |x: i32 |          x + 1  ;


nit, plus_2 should probably be x + 2 in the body

ahh, so this is because it's the second plus_ function, unfortuante clash. lemme tweak it

nikomatsakis · 2015-04-01T18:34:01Z

r+ -- seems like this can be improved over time, but it's pretty good

steveklabnik · 2015-04-01T19:21:16Z

@bors: r=nikomatsakis rollup

bors · 2015-04-01T19:21:17Z

📌 Commit eac94fa has been approved by nikomatsakis

@nikomatsakis

[rendered](https://github.com/steveklabnik/rust/blob/closure_docs/src/doc/trpl/closures.md) r? @nikomatsakis

rust-highfive assigned nikomatsakis Mar 20, 2015

glaebhoerl reviewed Mar 20, 2015
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mdinger mentioned this pull request Mar 23, 2015

Docs: guide copy edits, subjective improvements, and other suggestions #22954

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steveklabnik force-pushed the closure_docs branch from e8945f2 to 17dbace Compare March 31, 2015 03:16

steveklabnik force-pushed the closure_docs branch from 31fdf09 to 066dbf5 Compare March 31, 2015 22:02

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steveklabnik force-pushed the closure_docs branch from 066dbf5 to 156c204 Compare April 1, 2015 18:28

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Re-write closures chapter

eac94fa

steveklabnik force-pushed the closure_docs branch from 156c204 to eac94fa Compare April 1, 2015 19:21

alexcrichton added a commit to alexcrichton/rust that referenced this pull request Apr 1, 2015

rollup merge of rust-lang#23568: steveklabnik/closure_docs

232e79f

[rendered](https://github.com/steveklabnik/rust/blob/closure_docs/src/doc/trpl/closures.md) r? @nikomatsakis

alexcrichton merged commit eac94fa into rust-lang:master Apr 2, 2015

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Re-write closures chapter #23568

Re-write closures chapter #23568

steveklabnik commented Mar 20, 2015

glaebhoerl Mar 20, 2015

mdinger commented Mar 21, 2015

nikomatsakis Mar 23, 2015

steveklabnik Mar 24, 2015

steveklabnik Mar 31, 2015

steveklabnik commented Mar 24, 2015

Manishearth commented Mar 28, 2015

reem Mar 28, 2015

steveklabnik Mar 31, 2015

reem Mar 28, 2015

steveklabnik Mar 31, 2015

steveklabnik commented Mar 31, 2015

nikomatsakis commented Mar 31, 2015

nikomatsakis Apr 1, 2015

nikomatsakis Apr 1, 2015

steveklabnik Apr 1, 2015

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nikomatsakis commented Apr 1, 2015

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bors commented Apr 1, 2015

Re-write closures chapter #23568

Re-write closures chapter #23568

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steveklabnik commented Mar 20, 2015

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nikomatsakis commented Apr 1, 2015

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bors commented Apr 1, 2015