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Rollup merge of #24577 - steveklabnik:gh24573, r=alexcrichton

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Fixes #24573
This commit is contained in:
Steve Klabnik 2015-04-20 21:15:52 -04:00
commit 81b603e7a5
2 changed files with 46 additions and 115 deletions
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137
src/doc/reference.md
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@ -973,8 +973,7 @@ Use declarations support a number of convenient shortcuts:
An example of `use` declarations:
```
# #![feature(core)]
```rust
use std::option::Option::{Some, None};
use std::collections::hash_map::{self, HashMap};
@ -1031,16 +1030,17 @@ declarations.
An example of what will and will not work for `use` items:
```
# #![feature(core)]
# #![allow(unused_imports)]
use foo::core::iter; // good: foo is at the root of the crate
use foo::baz::foobaz; // good: foo is at the root of the crate
mod foo {
extern crate core;
use foo::core::iter; // good: foo is at crate root
// use core::iter; // bad: core is not at the crate root
mod example {
pub mod iter {}
}
use foo::example::iter; // good: foo is at crate root
// use example::iter; // bad: core is not at the crate root
use self::baz::foobaz; // good: self refers to module 'foo'
use foo::bar::foobar; // good: foo is at crate root
@ -1368,9 +1368,7 @@ a = Animal::Cat;
Enumeration constructors can have either named or unnamed fields:
```
# #![feature(struct_variant)]
# fn main() {
```rust
enum Animal {
Dog (String, f64),
Cat { name: String, weight: f64 }
@ -1378,7 +1376,6 @@ enum Animal {
let mut a: Animal = Animal::Dog("Cocoa".to_string(), 37.2);
a = Animal::Cat { name: "Spotty".to_string(), weight: 2.7 };
# }
```
In this example, `Cat` is a _struct-like enum variant_,
@ -1718,17 +1715,6 @@ Functions within external blocks are declared in the same way as other Rust
functions, with the exception that they may not have a body and are instead
terminated by a semicolon.
```
# #![feature(libc)]
extern crate libc;
use libc::{c_char, FILE};
extern {
fn fopen(filename: *const c_char, mode: *const c_char) -> *mut FILE;
}
# fn main() {}
```
Functions within external blocks may be called by Rust code, just like
functions defined in Rust. The Rust compiler automatically translates between
the Rust ABI and the foreign ABI.
@ -1739,7 +1725,7 @@ By default external blocks assume that the library they are calling uses the
standard C "cdecl" ABI. Other ABIs may be specified using an `abi` string, as
shown here:
```{.ignore}
```ignore
// Interface to the Windows API
extern "stdcall" { }
```
@ -3231,55 +3217,7 @@ expression.
In a pattern whose head expression has an `enum` type, a placeholder (`_`)
stands for a *single* data field, whereas a wildcard `..` stands for *all* the
fields of a particular variant. For example:
```
#![feature(box_patterns)]
#![feature(box_syntax)]
enum List<X> { Nil, Cons(X, Box<List<X>>) }
fn main() {
let x: List<i32> = List::Cons(10, box List::Cons(11, box List::Nil));
match x {
List::Cons(_, box List::Nil) => panic!("singleton list"),
List::Cons(..) => return,
List::Nil => panic!("empty list")
}
}
```
The first pattern matches lists constructed by applying `Cons` to any head
value, and a tail value of `box Nil`. The second pattern matches _any_ list
constructed with `Cons`, ignoring the values of its arguments. The difference
between `_` and `..` is that the pattern `C(_)` is only type-correct if `C` has
exactly one argument, while the pattern `C(..)` is type-correct for any enum
variant `C`, regardless of how many arguments `C` has.
Used inside an array pattern, `..` stands for any number of elements, when the
`advanced_slice_patterns` feature gate is turned on. This wildcard can be used
at most once for a given array, which implies that it cannot be used to
specifically match elements that are at an unknown distance from both ends of a
array, like `[.., 42, ..]`. If preceded by a variable name, it will bind the
corresponding slice to the variable. Example:
```
# #![feature(advanced_slice_patterns, slice_patterns)]
fn is_symmetric(list: &[u32]) -> bool {
match list {
[] | [_] => true,
[x, inside.., y] if x == y => is_symmetric(inside),
_ => false
}
}
fn main() {
let sym = &[0, 1, 4, 2, 4, 1, 0];
let not_sym = &[0, 1, 7, 2, 4, 1, 0];
assert!(is_symmetric(sym));
assert!(!is_symmetric(not_sym));
}
```
fields of a particular variant.
A `match` behaves differently depending on whether or not the head expression
is an [lvalue or an rvalue](#lvalues,-rvalues-and-temporaries). If the head
@ -3298,30 +3236,15 @@ the inside of the match.
An example of a `match` expression:
```
#![feature(box_patterns)]
#![feature(box_syntax)]
# fn process_pair(a: i32, b: i32) { }
# fn process_ten() { }
let x = 1;
enum List<X> { Nil, Cons(X, Box<List<X>>) }
fn main() {
let x: List<i32> = List::Cons(10, box List::Cons(11, box List::Nil));
match x {
List::Cons(a, box List::Cons(b, _)) => {
process_pair(a, b);
}
List::Cons(10, _) => {
process_ten();
}
List::Nil => {
return;
}
_ => {
panic!();
}
}
match x {
1 => println!("one"),
2 => println!("two"),
3 => println!("three"),
4 => println!("four"),
5 => println!("five"),
_ => println!("something else"),
}
```
@ -3334,28 +3257,12 @@ Subpatterns can also be bound to variables by the use of the syntax `variable @
subpattern`. For example:
```
#![feature(box_patterns)]
#![feature(box_syntax)]
let x = 1;
enum List { Nil, Cons(u32, Box<List>) }
fn is_sorted(list: &List) -> bool {
match *list {
List::Nil | List::Cons(_, box List::Nil) => true,
List::Cons(x, ref r @ box List::Cons(_, _)) => {
match *r {
box List::Cons(y, _) => (x <= y) && is_sorted(&**r),
_ => panic!()
}
}
}
match x {
e @ 1 ... 5 => println!("got a range element {}", e),
_ => println!("anything"),
}
fn main() {
let a = List::Cons(6, box List::Cons(7, box List::Cons(42, box List::Nil)));
assert!(is_sorted(&a));
}
```
Patterns can also dereference pointers by using the `&`, `&mut` and `box`

24
src/doc/trpl/slice-patterns.md
View file

@ -16,3 +16,27 @@ fn main() {
}
```
The `advanced_slice_patterns` gate lets you use `..` to indicate any number of
elements inside a pattern matching a slice. This wildcard can only be used once
for a given array. If there's an identifier before the `..`, the result of the
slice will be bound to that name. For example:
```rust
#![feature(advanced_slice_patterns, slice_patterns)]
fn is_symmetric(list: &[u32]) -> bool {
match list {
[] | [_] => true,
[x, inside.., y] if x == y => is_symmetric(inside),
_ => false
}
}
fn main() {
let sym = &[0, 1, 4, 2, 4, 1, 0];
assert!(is_symmetric(sym));
let not_sym = &[0, 1, 7, 2, 4, 1, 0];
assert!(!is_symmetric(not_sym));
}
```