extend the iterator tutorial + fix zero-size element vec iterators

doc/tutorial-container.md

@@ -205,3 +205,104 @@ println(fmt!("last: %?", it.next()));
 // the iterator is now fully consumed
 assert!(it.next().is_none());
 ~~~
+
+## Conversion
+
+Iterators offer generic conversion to containers with the `collect` adaptor:
+
+~~~
+let xs = [0, 1, 1, 2, 3, 5, 8];
+let ys = xs.rev_iter().skip(1).transform(|&x| x * 2).collect::<~[int]>();
+assert_eq!(ys, ~[10, 6, 4, 2, 2, 0]);
+~~~
+
+The method requires a type hint for the container type, if the surrounding code
+does not provide sufficient information.
+
+Containers can provide conversion from iterators through `collect` by
+implementing the `FromIterator` trait. For example, the implementation for
+vectors is as follows:
+
+~~~
+impl<A, T: Iterator<A>> FromIterator<A, T> for ~[A] {
+    pub fn from_iterator(iterator: &mut T) -> ~[A] {
+        let (lower, _) = iterator.size_hint();
+        let mut xs = with_capacity(lower);
+        for iterator.advance |x| {
+            xs.push(x);
+        }
+        xs
+    }
+}
+~~~
+
+### Size hints
+
+The `Iterator` trait provides a `size_hint` default method, returning a lower
+bound and optionally on upper bound on the length of the iterator:
+
+~~~
+fn size_hint(&self) -> (uint, Option<uint>) { (0, None) }
+~~~
+
+The vector implementation of `FromIterator` from above uses the lower bound
+to pre-allocate enough space to hold the minimum number of elements the
+iterator will yield.
+
+The default implementation is always correct, but it should be overridden if
+the iterator can provide better information.
+
+The `ZeroStream` from earlier can provide an exact lower and upper bound:
+
+~~~
+/// A stream of N zeroes
+struct ZeroStream {
+    priv remaining: uint
+}
+
+impl ZeroStream {
+    fn new(n: uint) -> ZeroStream {
+        ZeroStream { remaining: n }
+    }
+
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        (self.remaining, Some(self.remaining))
+    }
+}
+
+impl Iterator<int> for ZeroStream {
+    fn next(&mut self) -> Option<int> {
+        if self.remaining == 0 {
+            None
+        } else {
+            self.remaining -= 1;
+            Some(0)
+        }
+    }
+}
+~~~
+
+## Double-ended iterators
+
+The `DoubleEndedIterator` trait represents an iterator able to yield elements
+from either end of a range. It inherits from the `Iterator` trait and extends
+it with the `next_back` function.
+
+A `DoubleEndedIterator` can be flipped with the `invert` adaptor, returning
+another `DoubleEndedIterator` with `next` and `next_back` exchanged.
+
+~~~
+let xs = [1, 2, 3, 4, 5, 6];
+let mut it = xs.iter();
+println(fmt!("%?", it.next())); // prints `Some(&1)`
+println(fmt!("%?", it.next())); // prints `Some(&2)`
+println(fmt!("%?", it.next_back())); // prints `Some(&6)`
+
+// prints `5`, `4` and `3`
+for it.invert().advance |&x| {
+    println(fmt!("%?", x))
+}
+~~~
+
+The `rev_iter` and `mut_rev_iter` methods on vectors just return an inverted
+version of the standard immutable and mutable vector iterators.

src/libextra/bitv.rs

@@ -104,7 +104,7 @@ impl SmallBitv {
     }
 
     #[inline]
-    pub fn invert(&mut self) { self.bits = !self.bits; }
+    pub fn negate(&mut self) { self.bits = !self.bits; }
 }
 
 struct BigBitv {
@@ -160,7 +160,7 @@ impl BigBitv {
     }
 
     #[inline]
-    pub fn invert(&mut self) { for self.each_storage |w| { *w = !*w } }
+    pub fn negate(&mut self) { for self.each_storage |w| { *w = !*w } }
 
     #[inline]
     pub fn union(&mut self, b: &BigBitv, nbits: uint) -> bool {
@@ -366,9 +366,9 @@ impl Bitv {
 
     /// Invert all bits
     #[inline]
-    pub fn invert(&mut self) {
+    pub fn negate(&mut self) {
       match self.rep {
-        Small(ref mut b) => b.invert(),
+        Small(ref mut b) => b.negate(),
         Big(ref mut s) => for s.each_storage() |w| { *w = !*w } }
     }
 

src/libextra/flatpipes.rs

@@ -446,7 +446,7 @@ pub mod flatteners {
                               T: Decodable<D>>(
                               buf: &[u8])
                               -> T {
-        let buf = vec::to_owned(buf);
+        let buf = buf.to_owned();
         let buf_reader = @BufReader::new(buf);
         let reader = buf_reader as @Reader;
         let mut deser: D = FromReader::from_reader(reader);

src/libextra/getopts.rs

@@ -343,7 +343,7 @@ pub fn getopts(args: &[~str], opts: &[Opt]) -> Result {
         }
         i += 1;
     }
-    return Ok(Matches {opts: vec::to_owned(opts),
+    return Ok(Matches {opts: opts.to_owned(),
                vals: vals,
                free: free});
 }

src/libextra/md4.rs

@@ -28,7 +28,7 @@ pub fn md4(msg: &[u8]) -> Quad {
     let orig_len: u64 = (msg.len() * 8u) as u64;
 
     // pad message
-    let mut msg = vec::append(vec::to_owned(msg), [0x80u8]);
+    let mut msg = vec::append(msg.to_owned(), [0x80u8]);
     let mut bitlen = orig_len + 8u64;
     while (bitlen + 64u64) % 512u64 > 0u64 {
         msg.push(0u8);

src/libextra/num/bigint.rs

@@ -567,7 +567,7 @@ impl BigUint {
     /// Creates and initializes an BigUint.
 
     pub fn from_slice(slice: &[BigDigit]) -> BigUint {
-        return BigUint::new(vec::to_owned(slice));
+        return BigUint::new(slice.to_owned());
     }
 
     /// Creates and initializes an BigUint.

src/libextra/stats.rs

@@ -12,7 +12,6 @@ use sort;
 use std::cmp;
 use std::io;
 use std::num;
-use std::vec;
 
 // NB: this can probably be rewritten in terms of num::Num
 // to be less f64-specific.
@@ -200,13 +199,13 @@ impl<'self> Stats for &'self [f64] {
     }
 
     fn percentile(self, pct: f64) -> f64 {
-        let mut tmp = vec::to_owned(self);
+        let mut tmp = self.to_owned();
         sort::tim_sort(tmp);
         percentile_of_sorted(tmp, pct)
     }
 
     fn quartiles(self) -> (f64,f64,f64) {
-        let mut tmp = vec::to_owned(self);
+        let mut tmp = self.to_owned();
         sort::tim_sort(tmp);
         let a = percentile_of_sorted(tmp, 25.0);
         let b = percentile_of_sorted(tmp, 50.0);
@@ -251,7 +250,7 @@ priv fn percentile_of_sorted(sorted_samples: &[f64],
 ///
 /// See: http://en.wikipedia.org/wiki/Winsorising
 pub fn winsorize(samples: &mut [f64], pct: f64) {
-    let mut tmp = vec::to_owned(samples);
+    let mut tmp = samples.to_owned();
     sort::tim_sort(tmp);
     let lo = percentile_of_sorted(tmp, pct);
     let hi = percentile_of_sorted(tmp, 100.0-pct);

src/librustc/metadata/decoder.rs

@@ -714,7 +714,7 @@ pub fn maybe_get_item_ast(cdata: cmd, tcx: ty::ctxt,
     let item_doc = lookup_item(id, cdata.data);
     let path = {
         let item_path = item_path(item_doc);
-        vec::to_owned(item_path.init())
+        item_path.init().to_owned()
     };
     match decode_inlined_item(cdata, tcx, copy path, item_doc) {
       Some(ref ii) => csearch::found((/*bad*/copy *ii)),

src/librustc/metadata/encoder.rs

@@ -1659,7 +1659,7 @@ pub fn encode_metadata(parms: EncodeParams, crate: &crate) -> ~[u8] {
 
     let writer_bytes: &mut ~[u8] = wr.bytes;
 
-    vec::to_owned(metadata_encoding_version) +
+    metadata_encoding_version.to_owned() +
         flate::deflate_bytes(*writer_bytes)
 }
 

src/librustc/middle/check_match.rs

@@ -484,7 +484,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                 match cx.tcx.def_map.find(&pat_id) {
                     Some(&def_variant(_, id)) => {
                         if variant(id) == *ctor_id {
-                            Some(vec::to_owned(r.tail()))
+                            Some(r.tail().to_owned())
                         } else {
                             None
                         }
@@ -522,7 +522,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                             _ => fail!("type error")
                         };
                         if match_ {
-                            Some(vec::to_owned(r.tail()))
+                            Some(r.tail().to_owned())
                         } else {
                             None
                         }
@@ -569,7 +569,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                             _ => fail!("type error")
                         };
                         if match_ {
-                            Some(vec::to_owned(r.tail()))
+                            Some(r.tail().to_owned())
                         } else {
                             None
                         }
@@ -579,7 +579,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                             Some(args) => args,
                             None => vec::from_elem(arity, wild())
                         };
-                        Some(vec::append(args, vec::to_owned(r.tail())))
+                        Some(vec::append(args, r.tail()))
                     }
                     def_variant(_, _) => None,
 
@@ -591,7 +591,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                             Some(args) => new_args = args,
                             None => new_args = vec::from_elem(arity, wild())
                         }
-                        Some(vec::append(new_args, vec::to_owned(r.tail())))
+                        Some(vec::append(new_args, r.tail()))
                     }
                     _ => None
                 }
@@ -609,7 +609,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                                     _ => wild()
                                 }
                             });
-                            Some(vec::append(args, vec::to_owned(r.tail())))
+                            Some(vec::append(args, r.tail()))
                         } else {
                             None
                         }
@@ -640,7 +640,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                                 _ => wild()
                             }
                         }).collect();
-                        Some(vec::append(args, vec::to_owned(r.tail())))
+                        Some(vec::append(args, r.tail()))
                     }
                 }
             }
@@ -676,14 +676,14 @@ pub fn specialize(cx: &MatchCheckCtxt,
                     single => true,
                     _ => fail!("type error")
                 };
-                if match_ { Some(vec::to_owned(r.tail())) } else { None }
+                if match_ { Some(r.tail().to_owned()) } else { None }
             }
             pat_range(lo, hi) => {
                 let (c_lo, c_hi) = match *ctor_id {
                     val(ref v) => ((/*bad*/copy *v), (/*bad*/copy *v)),
                     range(ref lo, ref hi) =>
                         ((/*bad*/copy *lo), (/*bad*/copy *hi)),
-                    single => return Some(vec::to_owned(r.tail())),
+                    single => return Some(r.tail().to_owned()),
                     _ => fail!("type error")
                 };
                 let v_lo = eval_const_expr(cx.tcx, lo);
@@ -693,7 +693,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                 let m2 = compare_const_vals(&c_hi, &v_hi);
                 match (m1, m2) {
                     (Some(val1), Some(val2)) if val1 >= 0 && val2 <= 0 => {
-                        Some(vec::to_owned(r.tail()))
+                        Some(r.tail().to_owned())
                     },
                     (Some(_), Some(_)) => None,
                     _ => {
@@ -734,7 +734,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
 }
 
 pub fn default(cx: &MatchCheckCtxt, r: &[@pat]) -> Option<~[@pat]> {
-    if is_wild(cx, r[0]) { Some(vec::to_owned(r.tail())) }
+    if is_wild(cx, r[0]) { Some(r.tail().to_owned()) }
     else { None }
 }
 

src/librustc/middle/trans/adt.rs

@@ -47,7 +47,6 @@
 use std::container::Map;
 use std::libc::c_ulonglong;
 use std::option::{Option, Some, None};
-use std::vec;
 
 use lib::llvm::{ValueRef, True, IntEQ, IntNE};
 use middle::trans::_match;
@@ -219,7 +218,7 @@ fn mk_struct(cx: &mut CrateContext, tys: &[ty::t], packed: bool) -> Struct {
         size: machine::llsize_of_alloc(cx, llty_rec) /*bad*/as u64,
         align: machine::llalign_of_min(cx, llty_rec) /*bad*/as u64,
         packed: packed,
-        fields: vec::to_owned(tys)
+        fields: tys.to_owned(),
     }
 }
 

src/librustc/middle/ty.rs

@@ -3782,7 +3782,7 @@ pub fn item_path(cx: ctxt, id: ast::def_id) -> ast_map::path {
           }
 
           ast_map::node_variant(ref variant, _, path) => {
-            vec::append_one(vec::to_owned(path.init()),
+            vec::append_one(path.init().to_owned(),
                             ast_map::path_name((*variant).node.name))
           }
 

src/libstd/prelude.rs

@@ -47,8 +47,9 @@ pub use cmp::{Eq, ApproxEq, Ord, TotalEq, TotalOrd, Ordering, Less, Equal, Great
 pub use char::Char;
 pub use container::{Container, Mutable, Map, Set};
 pub use hash::Hash;
-pub use iter::{Times};
-pub use iterator::{Iterator, IteratorUtil, OrdIterator};
+pub use iter::Times;
+pub use iterator::{Iterator, IteratorUtil, DoubleEndedIterator, DoubleEndedIteratorUtil};
+pub use iterator::OrdIterator;
 pub use num::{Num, NumCast};
 pub use num::{Orderable, Signed, Unsigned, Round};
 pub use num::{Algebraic, Trigonometric, Exponential, Hyperbolic};

src/libstd/rand.rs

@@ -591,7 +591,7 @@ impl<R: Rng> RngUtil for R {
 
     /// Shuffle a vec
     fn shuffle<T:Copy>(&mut self, values: &[T]) -> ~[T] {
-        let mut m = vec::to_owned(values);
+        let mut m = values.to_owned();
         self.shuffle_mut(m);
         m
     }