Auto merge of #38610 - djzin:master, r=sfackler

Implementation of plan in issue #27787 for btree_range

Still some ergonomics to be worked on, the ::<str,_> is particularly unsightly

Author: bors

src/libcollections/btree/map.rs

@@ -17,7 +17,8 @@ use core::ops::Index;
 use core::{fmt, intrinsics, mem, ptr};
 
 use borrow::Borrow;
-use Bound::{self, Excluded, Included, Unbounded};
+use Bound::{Excluded, Included, Unbounded};
+use range::RangeArgument;
 
 use super::node::{self, Handle, NodeRef, marker};
 use super::search;
@@ -654,10 +655,12 @@ impl<K: Ord, V> BTreeMap<K, V> {
         self.fix_right_edge();
     }
 
-    /// Constructs a double-ended iterator over a sub-range of elements in the map, starting
-    /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
-    /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
-    /// Thus range(Unbounded, Unbounded) will yield the whole collection.
+    /// Constructs a double-ended iterator over a sub-range of elements in the map.
+    /// The simplest way is to use the range synax `min..max`, thus `range(min..max)` will
+    /// yield elements from min (inclusive) to max (exclusive).
+    /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
+    /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
+    /// range from 4 to 10.
     ///
     /// # Examples
     ///
@@ -667,26 +670,25 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// #![feature(btree_range, collections_bound)]
     ///
     /// use std::collections::BTreeMap;
-    /// use std::collections::Bound::{Included, Unbounded};
+    /// use std::collections::Bound::Included;
     ///
     /// let mut map = BTreeMap::new();
     /// map.insert(3, "a");
     /// map.insert(5, "b");
     /// map.insert(8, "c");
-    /// for (&key, &value) in map.range(Included(&4), Included(&8)) {
+    /// for (&key, &value) in map.range((Included(&4), Included(&8))) {
     ///     println!("{}: {}", key, value);
     /// }
-    /// assert_eq!(Some((&5, &"b")), map.range(Included(&4), Unbounded).next());
+    /// assert_eq!(Some((&5, &"b")), map.range(4..).next());
     /// ```
     #[unstable(feature = "btree_range",
                reason = "matches collection reform specification, waiting for dust to settle",
                issue = "27787")]
-    pub fn range<Min: ?Sized + Ord, Max: ?Sized + Ord>(&self,
-                                                       min: Bound<&Min>,
-                                                       max: Bound<&Max>)
-                                                       -> Range<K, V>
-        where K: Borrow<Min> + Borrow<Max>
+    pub fn range<T: ?Sized, R>(&self, range: R) -> Range<K, V>
+        where T: Ord, K: Borrow<T>, R: RangeArgument<T>
     {
+        let min = range.start();
+        let max = range.end();
         let front = match min {
             Included(key) => {
                 match search::search_tree(self.root.as_ref(), key) {
@@ -745,25 +747,26 @@ impl<K: Ord, V> BTreeMap<K, V> {
         }
     }
 
-    /// Constructs a mutable double-ended iterator over a sub-range of elements in the map, starting
-    /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
-    /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
-    /// Thus range(Unbounded, Unbounded) will yield the whole collection.
+    /// Constructs a mutable double-ended iterator over a sub-range of elements in the map.
+    /// The simplest way is to use the range synax `min..max`, thus `range(min..max)` will
+    /// yield elements from min (inclusive) to max (exclusive).
+    /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
+    /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
+    /// range from 4 to 10.
     ///
     /// # Examples
     ///
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(btree_range, collections_bound)]
+    /// #![feature(btree_range)]
     ///
     /// use std::collections::BTreeMap;
-    /// use std::collections::Bound::{Included, Excluded};
     ///
     /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
     ///                                                                       .map(|&s| (s, 0))
     ///                                                                       .collect();
-    /// for (_, balance) in map.range_mut(Included("B"), Excluded("Cheryl")) {
+    /// for (_, balance) in map.range_mut("B".."Cheryl") {
     ///     *balance += 100;
     /// }
     /// for (name, balance) in &map {
@@ -773,12 +776,11 @@ impl<K: Ord, V> BTreeMap<K, V> {
     #[unstable(feature = "btree_range",
                reason = "matches collection reform specification, waiting for dust to settle",
                issue = "27787")]
-    pub fn range_mut<Min: ?Sized + Ord, Max: ?Sized + Ord>(&mut self,
-                                                           min: Bound<&Min>,
-                                                           max: Bound<&Max>)
-                                                           -> RangeMut<K, V>
-        where K: Borrow<Min> + Borrow<Max>
+    pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<K, V>
+        where T: Ord, K: Borrow<T>, R: RangeArgument<T>
     {
+        let min = range.start();
+        let max = range.end();
         let root1 = self.root.as_mut();
         let root2 = unsafe { ptr::read(&root1) };
 

src/libcollections/btree/set.rs

@@ -21,7 +21,7 @@ use core::ops::{BitOr, BitAnd, BitXor, Sub};
 use borrow::Borrow;
 use btree_map::{BTreeMap, Keys};
 use super::Recover;
-use Bound;
+use range::RangeArgument;
 
 // FIXME(conventions): implement bounded iterators
 
@@ -207,38 +207,37 @@ impl<T> BTreeSet<T> {
 }
 
 impl<T: Ord> BTreeSet<T> {
-    /// Constructs a double-ended iterator over a sub-range of elements in the set, starting
-    /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
-    /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
-    /// Thus range(Unbounded, Unbounded) will yield the whole collection.
+    /// Constructs a double-ended iterator over a sub-range of elements in the set.
+    /// The simplest way is to use the range synax `min..max`, thus `range(min..max)` will
+    /// yield elements from min (inclusive) to max (exclusive).
+    /// The range may also be entered as `(Bound<T>, Bound<T>)`, so for example
+    /// `range((Excluded(4), Included(10)))` will yield a left-exclusive, right-inclusive
+    /// range from 4 to 10.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(btree_range, collections_bound)]
     ///
     /// use std::collections::BTreeSet;
-    /// use std::collections::Bound::{Included, Unbounded};
+    /// use std::collections::Bound::Included;
     ///
     /// let mut set = BTreeSet::new();
     /// set.insert(3);
     /// set.insert(5);
     /// set.insert(8);
-    /// for &elem in set.range(Included(&4), Included(&8)) {
+    /// for &elem in set.range((Included(&4), Included(&8))) {
     ///     println!("{}", elem);
     /// }
-    /// assert_eq!(Some(&5), set.range(Included(&4), Unbounded).next());
+    /// assert_eq!(Some(&5), set.range(4..).next());
     /// ```
     #[unstable(feature = "btree_range",
                reason = "matches collection reform specification, waiting for dust to settle",
                issue = "27787")]
-    pub fn range<'a, Min: ?Sized + Ord, Max: ?Sized + Ord>(&'a self,
-                                                           min: Bound<&Min>,
-                                                           max: Bound<&Max>)
-                                                           -> Range<'a, T>
-        where T: Borrow<Min> + Borrow<Max>
+    pub fn range<K: ?Sized, R>(&self, range: R) -> Range<T>
+        where K: Ord, T: Borrow<K>, R: RangeArgument<K>
     {
-        Range { iter: self.map.range(min, max) }
+        Range { iter: self.map.range(range) }
     }
 }
 

src/libcollections/range.rs

@@ -15,78 +15,120 @@
 //! Range syntax.
 
 use core::ops::{RangeFull, Range, RangeTo, RangeFrom};
+use Bound::{self, Excluded, Included, Unbounded};
 
 /// **RangeArgument** is implemented by Rust's built-in range types, produced
 /// by range syntax like `..`, `a..`, `..b` or `c..d`.
-pub trait RangeArgument<T> {
-    /// Start index (inclusive)
+pub trait RangeArgument<T: ?Sized> {
+    /// Start index bound
     ///
-    /// Return start value if present, else `None`.
+    /// Return start value as a `Bound`
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(collections)]
     /// #![feature(collections_range)]
+    /// #![feature(collections_bound)]
     ///
     /// extern crate collections;
     ///
     /// # fn main() {
     /// use collections::range::RangeArgument;
+    /// use collections::Bound::*;
     ///
-    /// assert_eq!((..10).start(), None);
-    /// assert_eq!((3..10).start(), Some(&3));
+    /// assert_eq!((..10).start(), Unbounded);
+    /// assert_eq!((3..10).start(), Included(&3));
     /// # }
     /// ```
-    fn start(&self) -> Option<&T> {
-        None
-    }
+    fn start(&self) -> Bound<&T>;
 
-    /// End index (exclusive)
+    /// End index bound
     ///
-    /// Return end value if present, else `None`.
+    /// Return end value as a `Bound`
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(collections)]
     /// #![feature(collections_range)]
+    /// #![feature(collections_bound)]
     ///
     /// extern crate collections;
     ///
     /// # fn main() {
     /// use collections::range::RangeArgument;
+    /// use collections::Bound::*;
     ///
-    /// assert_eq!((3..).end(), None);
-    /// assert_eq!((3..10).end(), Some(&10));
+    /// assert_eq!((3..).end(), Unbounded);
+    /// assert_eq!((3..10).end(), Excluded(&10));
     /// # }
     /// ```
-    fn end(&self) -> Option<&T> {
-        None
-    }
+    fn end(&self) -> Bound<&T>;
 }
 
 // FIXME add inclusive ranges to RangeArgument
 
-impl<T> RangeArgument<T> for RangeFull {}
+impl<T: ?Sized> RangeArgument<T> for RangeFull {
+    fn start(&self) -> Bound<&T> {
+        Unbounded
+    }
+    fn end(&self) -> Bound<&T> {
+        Unbounded
+    }
+}
 
 impl<T> RangeArgument<T> for RangeFrom<T> {
-    fn start(&self) -> Option<&T> {
-        Some(&self.start)
+    fn start(&self) -> Bound<&T> {
+        Included(&self.start)
+    }
+    fn end(&self) -> Bound<&T> {
+        Unbounded
     }
 }
 
 impl<T> RangeArgument<T> for RangeTo<T> {
-    fn end(&self) -> Option<&T> {
-        Some(&self.end)
+    fn start(&self) -> Bound<&T> {
+        Unbounded
+    }
+    fn end(&self) -> Bound<&T> {
+        Excluded(&self.end)
     }
 }
 
 impl<T> RangeArgument<T> for Range<T> {
-    fn start(&self) -> Option<&T> {
-        Some(&self.start)
+    fn start(&self) -> Bound<&T> {
+        Included(&self.start)
     }
-    fn end(&self) -> Option<&T> {
-        Some(&self.end)
+    fn end(&self) -> Bound<&T> {
+        Excluded(&self.end)
+    }
+}
+
+impl<T> RangeArgument<T> for (Bound<T>, Bound<T>) {
+    fn start(&self) -> Bound<&T> {
+        match *self {
+            (Included(ref start), _) => Included(start),
+            (Excluded(ref start), _) => Excluded(start),
+            (Unbounded, _)           => Unbounded,
+        }
+    }
+
+    fn end(&self) -> Bound<&T> {
+        match *self {
+            (_, Included(ref end)) => Included(end),
+            (_, Excluded(ref end)) => Excluded(end),
+            (_, Unbounded)         => Unbounded,
+        }
+    }
+}
+
+impl<'a, T: ?Sized + 'a> RangeArgument<T> for (Bound<&'a T>, Bound<&'a T>) {
+    fn start(&self) -> Bound<&T> {
+        self.0
+    }
+
+    fn end(&self) -> Bound<&T> {
+        self.1
     }
 }

src/libcollections/string.rs

@@ -68,6 +68,7 @@ use std_unicode::str as unicode_str;
 
 use borrow::{Cow, ToOwned};
 use range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 use str::{self, FromStr, Utf8Error, Chars};
 use vec::Vec;
 use boxed::Box;
@@ -1350,8 +1351,16 @@ impl String {
         // Because the range removal happens in Drop, if the Drain iterator is leaked,
         // the removal will not happen.
         let len = self.len();
-        let start = *range.start().unwrap_or(&0);
-        let end = *range.end().unwrap_or(&len);
+        let start = match range.start() {
+            Included(&n) => n,
+            Excluded(&n) => n + 1,
+            Unbounded => 0,
+        };
+        let end = match range.end() {
+            Included(&n) => n + 1,
+            Excluded(&n) => n,
+            Unbounded => len,
+        };
 
         // Take out two simultaneous borrows. The &mut String won't be accessed
         // until iteration is over, in Drop.

src/libcollections/vec.rs

@@ -84,6 +84,7 @@ use core::ptr::Shared;
 use core::slice;
 
 use super::range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 
 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
 ///
@@ -1060,8 +1061,16 @@ impl<T> Vec<T> {
         // the hole, and the vector length is restored to the new length.
         //
         let len = self.len();
-        let start = *range.start().unwrap_or(&0);
-        let end = *range.end().unwrap_or(&len);
+        let start = match range.start() {
+            Included(&n) => n,
+            Excluded(&n) => n + 1,
+            Unbounded    => 0,
+        };
+        let end = match range.end() {
+            Included(&n) => n + 1,
+            Excluded(&n) => n,
+            Unbounded    => len,
+        };
         assert!(start <= end);
         assert!(end <= len);
 

src/libcollections/vec_deque.rs

@@ -33,6 +33,7 @@ use core::cmp;
 use alloc::raw_vec::RawVec;
 
 use super::range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 use super::vec::Vec;
 
 const INITIAL_CAPACITY: usize = 7; // 2^3 - 1
@@ -852,8 +853,16 @@ impl<T> VecDeque<T> {
         // and the head/tail values will be restored correctly.
         //
         let len = self.len();
-        let start = *range.start().unwrap_or(&0);
-        let end = *range.end().unwrap_or(&len);
+        let start = match range.start() {
+            Included(&n) => n,
+            Excluded(&n) => n + 1,
+            Unbounded    => 0,
+        };
+        let end = match range.end() {
+            Included(&n) => n + 1,
+            Excluded(&n) => n,
+            Unbounded    => len,
+        };
         assert!(start <= end, "drain lower bound was too large");
         assert!(end <= len, "drain upper bound was too large");