Revised core::ops::range::* docs

Part of #29365.
* Strenghtened summary/explanation split, making phrasings more parallel
* Added links throughout
* Fixed some example formatting & removed extraneous `fn main()`s (or hid
  then when needed because of `#![features]`.
* Emphasized note on `RangeFrom`'s `Iterator` implementation
* Added summary sentences to (unstable) `contains` methods

1 files changed, 120 insertions, 95 deletions

diff --git a/src/libcore/ops/range.rs b/src/libcore/ops/range.rs
index 33258b7a875..6a405cfdb98 100644
--- a/src/libcore/ops/range.rs
+++ b/src/libcore/ops/range.rs
@@ -10,10 +10,10 @@
 
 use fmt;
 
-/// An unbounded range. Use `..` (two dots) for its shorthand.
+/// An unbounded range (`..`).
 ///
-/// Its primary use case is slicing index. It cannot serve as an iterator
-/// because it doesn't have a starting point.
+/// `RangeFull` is primarily used as a [slicing index], it's shorthand is `..`.
+/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
 ///
 /// # Examples
 ///
@@ -23,8 +23,8 @@ use fmt;
 /// assert_eq!((..), std::ops::RangeFull);
 /// ```
 ///
-/// It does not have an `IntoIterator` implementation, so you can't use it in a
-/// `for` loop directly. This won't compile:
+/// It does not have an [`IntoIterator`] implementation, so you can't use it in
+/// a `for` loop directly. This won't compile:
 ///
 /// ```compile_fail,E0277
 /// for i in .. {
@@ -32,7 +32,7 @@ use fmt;
 /// }
 /// ```
 ///
-/// Used as a slicing index, `RangeFull` produces the full array as a slice.
+/// Used as a [slicing index], `RangeFull` produces the full array as a slice.
 ///
 /// ```
 /// let arr = [0, 1, 2, 3];
@@ -41,6 +41,10 @@ use fmt;
 /// assert_eq!(arr[1.. ], [  1,2,3]);
 /// assert_eq!(arr[1..3], [  1,2  ]);
 /// ```
+///
+/// [`IntoIterator`]: ../iter/trait.Iterator.html
+/// [`Iterator`]: ../iter/trait.IntoIterator.html
+/// [slicing index]: ../slice/trait.SliceIndex.html
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RangeFull;
@@ -52,24 +56,23 @@ impl fmt::Debug for RangeFull {
     }
 }
 
-/// A (half-open) range which is bounded at both ends: { x | start <= x < end }.
-/// Use `start..end` (two dots) for its shorthand.
+/// A (half-open) range bounded inclusively below and exclusively above
+/// (`start..end`).
 ///
-/// See the [`contains`](#method.contains) method for its characterization.
+/// The `Range` `start..end` contains all values with `x >= start` and
+/// `x < end`.
 ///
 /// # Examples
 ///
 /// ```
-/// fn main() {
-///     assert_eq!((3..5), std::ops::Range{ start: 3, end: 5 });
-///     assert_eq!(3+4+5, (3..6).sum());
-///
-///     let arr = [0, 1, 2, 3];
-///     assert_eq!(arr[ .. ], [0,1,2,3]);
-///     assert_eq!(arr[ ..3], [0,1,2  ]);
-///     assert_eq!(arr[1.. ], [  1,2,3]);
-///     assert_eq!(arr[1..3], [  1,2  ]);  // Range
-/// }
+/// assert_eq!((3..5), std::ops::Range { start: 3, end: 5 });
+/// assert_eq!(3 + 4 + 5, (3..6).sum());
+///
+/// let arr = [0, 1, 2, 3];
+/// assert_eq!(arr[ .. ], [0,1,2,3]);
+/// assert_eq!(arr[ ..3], [0,1,2  ]);
+/// assert_eq!(arr[1.. ], [  1,2,3]);
+/// assert_eq!(arr[1..3], [  1,2  ]);  // Range
 /// ```
 #[derive(Clone, PartialEq, Eq, Hash)]  // not Copy -- see #27186
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -91,49 +94,51 @@ impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> {
 
 #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
 impl<Idx: PartialOrd<Idx>> Range<Idx> {
+    /// Returns `true` if `item` is contained in the range.
+    ///
     /// # Examples
     ///
     /// ```
     /// #![feature(range_contains)]
-    /// fn main() {
-    ///     assert!( ! (3..5).contains(2));
-    ///     assert!(   (3..5).contains(3));
-    ///     assert!(   (3..5).contains(4));
-    ///     assert!( ! (3..5).contains(5));
     ///
-    ///     assert!( ! (3..3).contains(3));
-    ///     assert!( ! (3..2).contains(3));
-    /// }
+    /// # fn main() {
+    /// assert!(!(3..5).contains(2));
+    /// assert!( (3..5).contains(3));
+    /// assert!( (3..5).contains(4));
+    /// assert!(!(3..5).contains(5));
+    ///
+    /// assert!(!(3..3).contains(3));
+    /// assert!(!(3..2).contains(3));
+    /// # }
     /// ```
     pub fn contains(&self, item: Idx) -> bool {
         (self.start <= item) && (item < self.end)
     }
 }
 
-/// A range which is only bounded below: { x | start <= x }.
-/// Use `start..` for its shorthand.
+/// A range only bounded inclusively below (`start..`).
 ///
-/// See the [`contains`](#method.contains) method for its characterization.
+/// The `RangeFrom` `start..` contains all values with `x >= start`.
 ///
-/// Note: Currently, no overflow checking is done for the iterator
+/// *Note*: Currently, no overflow checking is done for the [`Iterator`]
 /// implementation; if you use an integer range and the integer overflows, it
-/// might panic in debug mode or create an endless loop in release mode. This
-/// overflow behavior might change in the future.
+/// might panic in debug mode or create an endless loop in release mode. **This
+/// overflow behavior might change in the future.**
 ///
 /// # Examples
 ///
 /// ```
-/// fn main() {
-///     assert_eq!((2..), std::ops::RangeFrom{ start: 2 });
-///     assert_eq!(2+3+4, (2..).take(3).sum());
-///
-///     let arr = [0, 1, 2, 3];
-///     assert_eq!(arr[ .. ], [0,1,2,3]);
-///     assert_eq!(arr[ ..3], [0,1,2  ]);
-///     assert_eq!(arr[1.. ], [  1,2,3]);  // RangeFrom
-///     assert_eq!(arr[1..3], [  1,2  ]);
-/// }
+/// assert_eq!((2..), std::ops::RangeFrom { start: 2 });
+/// assert_eq!(2 + 3 + 4, (2..).take(3).sum());
+///
+/// let arr = [0, 1, 2, 3];
+/// assert_eq!(arr[ .. ], [0,1,2,3]);
+/// assert_eq!(arr[ ..3], [0,1,2  ]);
+/// assert_eq!(arr[1.. ], [  1,2,3]);  // RangeFrom
+/// assert_eq!(arr[1..3], [  1,2  ]);
 /// ```
+///
+/// [`Iterator`]: ../iter/trait.IntoIterator.html
 #[derive(Clone, PartialEq, Eq, Hash)]  // not Copy -- see #27186
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RangeFrom<Idx> {
@@ -151,38 +156,39 @@ impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> {
 
 #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
 impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
+    /// Returns `true` if `item` is contained in the range.
+    ///
     /// # Examples
     ///
     /// ```
     /// #![feature(range_contains)]
-    /// fn main() {
-    ///     assert!( ! (3..).contains(2));
-    ///     assert!(   (3..).contains(3));
-    ///     assert!(   (3..).contains(1_000_000_000));
-    /// }
+    ///
+    /// # fn main() {
+    /// assert!(!(3..).contains(2));
+    /// assert!( (3..).contains(3));
+    /// assert!( (3..).contains(1_000_000_000));
+    /// # }
     /// ```
     pub fn contains(&self, item: Idx) -> bool {
         (self.start <= item)
     }
 }
 
-/// A range which is only bounded above: { x | x < end }.
-/// Use `..end` (two dots) for its shorthand.
-///
-/// See the [`contains`](#method.contains) method for its characterization.
+/// A range only bounded exclusively above (`..end`).
 ///
-/// It cannot serve as an iterator because it doesn't have a starting point.
+/// The `RangeTo` `..end` contains all values with `x < end`.
+/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
 ///
 /// # Examples
 ///
-/// The `..{integer}` syntax is a `RangeTo`:
+/// The `..end` syntax is a `RangeTo`:
 ///
 /// ```
-/// assert_eq!((..5), std::ops::RangeTo{ end: 5 });
+/// assert_eq!((..5), std::ops::RangeTo { end: 5 });
 /// ```
 ///
-/// It does not have an `IntoIterator` implementation, so you can't use it in a
-/// `for` loop directly. This won't compile:
+/// It does not have an [`IntoIterator`] implementation, so you can't use it in
+/// a `for` loop directly. This won't compile:
 ///
 /// ```compile_fail,E0277
 /// for i in ..5 {
@@ -190,7 +196,7 @@ impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
 /// }
 /// ```
 ///
-/// When used as a slicing index, `RangeTo` produces a slice of all array
+/// When used as a [slicing index], `RangeTo` produces a slice of all array
 /// elements before the index indicated by `end`.
 ///
 /// ```
@@ -200,6 +206,10 @@ impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
 /// assert_eq!(arr[1.. ], [  1,2,3]);
 /// assert_eq!(arr[1..3], [  1,2  ]);
 /// ```
+///
+/// [`IntoIterator`]: ../iter/trait.Iterator.html
+/// [`Iterator`]: ../iter/trait.IntoIterator.html
+/// [slicing index]: ../slice/trait.SliceIndex.html
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RangeTo<Idx> {
@@ -217,38 +227,42 @@ impl<Idx: fmt::Debug> fmt::Debug for RangeTo<Idx> {
 
 #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
 impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
+    /// Returns `true` if `item` is contained in the range.
+    ///
     /// # Examples
     ///
     /// ```
     /// #![feature(range_contains)]
-    /// fn main() {
-    ///     assert!(   (..5).contains(-1_000_000_000));
-    ///     assert!(   (..5).contains(4));
-    ///     assert!( ! (..5).contains(5));
-    /// }
+    ///
+    /// # fn main() {
+    /// assert!( (..5).contains(-1_000_000_000));
+    /// assert!( (..5).contains(4));
+    /// assert!(!(..5).contains(5));
+    /// # }
     /// ```
     pub fn contains(&self, item: Idx) -> bool {
         (item < self.end)
     }
 }
 
-/// An inclusive range which is bounded at both ends: { x | start <= x <= end }.
-/// Use `start...end` (three dots) for its shorthand.
+/// An range bounded inclusively below and above (`start...end`).
 ///
-/// See the [`contains`](#method.contains) method for its characterization.
+/// The `RangeInclusive` `start...end` contains all values with `x >= start`
+/// and `x <= end`.
 ///
 /// # Examples
 ///
 /// ```
 /// #![feature(inclusive_range,inclusive_range_syntax)]
-/// fn main() {
-///     assert_eq!((3...5), std::ops::RangeInclusive{ start: 3, end: 5 });
-///     assert_eq!(3+4+5, (3...5).sum());
 ///
-///     let arr = [0, 1, 2, 3];
-///     assert_eq!(arr[ ...2], [0,1,2  ]);
-///     assert_eq!(arr[1...2], [  1,2  ]);  // RangeInclusive
-/// }
+/// # fn main() {
+/// assert_eq!((3...5), std::ops::RangeInclusive { start: 3, end: 5 });
+/// assert_eq!(3 + 4 + 5, (3...5).sum());
+///
+/// let arr = [0, 1, 2, 3];
+/// assert_eq!(arr[ ...2], [0,1,2  ]);
+/// assert_eq!(arr[1...2], [  1,2  ]);  // RangeInclusive
+/// # }
 /// ```
 #[derive(Clone, PartialEq, Eq, Hash)]  // not Copy -- see #27186
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
@@ -274,43 +288,44 @@ impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
 
 #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
 impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
+    /// Returns `true` if `item` is contained in the range.
+    ///
     /// # Examples
     ///
     /// ```
     /// #![feature(range_contains,inclusive_range_syntax)]
-    /// fn main() {
-    ///     assert!( ! (3...5).contains(2));
-    ///     assert!(   (3...5).contains(3));
-    ///     assert!(   (3...5).contains(4));
-    ///     assert!(   (3...5).contains(5));
-    ///     assert!( ! (3...5).contains(6));
     ///
-    ///     assert!(   (3...3).contains(3));
-    ///     assert!( ! (3...2).contains(3));
-    /// }
+    /// # fn main() {
+    /// assert!(!(3...5).contains(2));
+    /// assert!( (3...5).contains(3));
+    /// assert!( (3...5).contains(4));
+    /// assert!( (3...5).contains(5));
+    /// assert!(!(3...5).contains(6));
+    ///
+    /// assert!( (3...3).contains(3));
+    /// assert!(!(3...2).contains(3));
+    /// # }
     /// ```
     pub fn contains(&self, item: Idx) -> bool {
         self.start <= item && item <= self.end
     }
 }
 
-/// An inclusive range which is only bounded above: { x | x <= end }.
-/// Use `...end` (three dots) for its shorthand.
-///
-/// See the [`contains`](#method.contains) method for its characterization.
+/// A range only bounded inclusively above (`...end`).
 ///
-/// It cannot serve as an iterator because it doesn't have a starting point.
+/// The `RangeToInclusive` `...end` contains all values with `x <= end`.
+/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
 ///
 /// # Examples
 ///
-/// The `...{integer}` syntax is a `RangeToInclusive`:
+/// The `...end` syntax is a `RangeToInclusive`:
 ///
 /// ```
 /// #![feature(inclusive_range,inclusive_range_syntax)]
 /// assert_eq!((...5), std::ops::RangeToInclusive{ end: 5 });
 /// ```
 ///
-/// It does not have an `IntoIterator` implementation, so you can't use it in a
+/// It does not have an [`IntoIterator`] implementation, so you can't use it in a
 /// `for` loop directly. This won't compile:
 ///
 /// ```compile_fail,E0277
@@ -320,15 +335,22 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
 /// }
 /// ```
 ///
-/// When used as a slicing index, `RangeToInclusive` produces a slice of all
+/// When used as a [slicing index], `RangeToInclusive` produces a slice of all
 /// array elements up to and including the index indicated by `end`.
 ///
 /// ```
 /// #![feature(inclusive_range_syntax)]
+///
+/// # fn main() {
 /// let arr = [0, 1, 2, 3];
 /// assert_eq!(arr[ ...2], [0,1,2  ]);  // RangeToInclusive
 /// assert_eq!(arr[1...2], [  1,2  ]);
+/// # }
 /// ```
+///
+/// [`IntoIterator`]: ../iter/trait.Iterator.html
+/// [`Iterator`]: ../iter/trait.IntoIterator.html
+/// [slicing index]: ../slice/trait.SliceIndex.html
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
 pub struct RangeToInclusive<Idx> {
@@ -348,15 +370,18 @@ impl<Idx: fmt::Debug> fmt::Debug for RangeToInclusive<Idx> {
 
 #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
 impl<Idx: PartialOrd<Idx>> RangeToInclusive<Idx> {
+    /// Returns `true` if `item` is contained in the range.
+    ///
     /// # Examples
     ///
     /// ```
     /// #![feature(range_contains,inclusive_range_syntax)]
-    /// fn main() {
-    ///     assert!(   (...5).contains(-1_000_000_000));
-    ///     assert!(   (...5).contains(5));
-    ///     assert!( ! (...5).contains(6));
-    /// }
+    ///
+    /// # fn main() {
+    /// assert!( (...5).contains(-1_000_000_000));
+    /// assert!( (...5).contains(5));
+    /// assert!(!(...5).contains(6));
+    /// # }
     /// ```
     pub fn contains(&self, item: Idx) -> bool {
         (item <= self.end)