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auto merge of #15787 : treeman/rust/hashmap-doc, r=alexcrichton

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Add an example showing how to use the map with a custom type. Fill in
examples for methods  without ones.

Also move `pop_equiv` next to related public methods, to not create a
duplicate trait in the docs.
This commit is contained in:
bors 2014-07-25 23:01:16 +00:00
commit 92c97059ff
1 changed files with 337 additions and 48 deletions
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385
src/libstd/collections/hashmap.rs
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@ -693,7 +693,7 @@ impl DefaultResizePolicy {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashMap;
///
/// // type inference lets us omit an explicit type signature (which
@ -729,6 +729,30 @@ impl DefaultResizePolicy {
/// println!("{}: \"{}\"", *book, *review);
/// }
/// ```
///
/// The easiest way to use `HashMap` with a custom type is to derive `Eq` and `Hash`.
/// We must also derive `PartialEq`.
///
/// ```
/// use std::collections::HashMap;
///
/// #[deriving(Hash, Eq, PartialEq, Show)]
/// struct Viking<'a> {
/// name: &'a str,
/// power: uint,
/// }
///
/// let mut vikings = HashMap::new();
///
/// vikings.insert("Norway", Viking { name: "Einar", power: 9u });
/// vikings.insert("Denmark", Viking { name: "Olaf", power: 4u });
/// vikings.insert("Iceland", Viking { name: "Harald", power: 8u });
///
/// // Use derived implementation to print the vikings.
/// for (land, viking) in vikings.iter() {
/// println!("{} at {}", viking, land);
/// }
/// ```
#[deriving(Clone)]
pub struct HashMap<K, V, H = RandomSipHasher> {
// All hashes are keyed on these values, to prevent hash collision attacks.
@ -906,28 +930,10 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
// earlier.
return Some(retval);
}
/// Like `pop`, but can operate on any type that is equivalent to a key.
#[experimental]
pub fn pop_equiv<Q:Hash<S> + Equiv<K>>(&mut self, k: &Q) -> Option<V> {
if self.table.size() == 0 {
return None
}
let potential_new_size = self.table.size() - 1;
self.make_some_room(potential_new_size);
let starting_index = match self.search_equiv(k) {
Some(idx) => idx,
None => return None,
};
self.pop_internal(starting_index)
}
}
impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> Collection for HashMap<K, V, H> {
/// Return the number of elements in the map
/// Return the number of elements in the map.
fn len(&self) -> uint { self.table.size() }
}
@ -1032,12 +1038,26 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> MutableMap<K, V> for HashMap<K, V, H>
impl<K: Hash + Eq, V> HashMap<K, V, RandomSipHasher> {
/// Create an empty HashMap.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// let mut map: HashMap<&str, int> = HashMap::new();
/// ```
#[inline]
pub fn new() -> HashMap<K, V, RandomSipHasher> {
HashMap::with_capacity(INITIAL_CAPACITY)
}
/// Creates an empty hash map with the given initial capacity.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// let mut map: HashMap<&str, int> = HashMap::with_capacity(10);
/// ```
#[inline]
pub fn with_capacity(capacity: uint) -> HashMap<K, V, RandomSipHasher> {
let hasher = RandomSipHasher::new();
@ -1049,6 +1069,17 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// Creates an empty hashmap which will use the given hasher to hash keys.
///
/// The creates map has the default initial capacity.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// use std::hash::sip::SipHasher;
///
/// let h = SipHasher::new();
/// let mut map = HashMap::with_hasher(h);
/// map.insert(1i, 2u);
/// ```
#[inline]
pub fn with_hasher(hasher: H) -> HashMap<K, V, H> {
HashMap::with_capacity_and_hasher(INITIAL_CAPACITY, hasher)
@ -1061,6 +1092,17 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// is designed to allow HashMaps to be resistant to attacks that
/// cause many collisions and very poor performance. Setting it
/// manually using this function can expose a DoS attack vector.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// use std::hash::sip::SipHasher;
///
/// let h = SipHasher::new();
/// let mut map = HashMap::with_capacity_and_hasher(10, h);
/// map.insert(1i, 2u);
/// ```
#[inline]
pub fn with_capacity_and_hasher(capacity: uint, hasher: H) -> HashMap<K, V, H> {
let cap = num::next_power_of_two(max(INITIAL_CAPACITY, capacity));
@ -1077,6 +1119,12 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
///
/// This function has no effect on the operational semantics of the
/// hashtable, only on performance.
///
/// ```
/// use std::collections::HashMap;
/// let mut map: HashMap<&str, int> = HashMap::new();
/// map.reserve(10);
/// ```
pub fn reserve(&mut self, new_minimum_capacity: uint) {
let cap = num::next_power_of_two(
max(INITIAL_CAPACITY, new_minimum_capacity));
@ -1241,12 +1289,38 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// Return the value corresponding to the key in the map, or insert
/// and return the value if it doesn't exist.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// let mut map = HashMap::new();
///
/// // Insert 1i with key "a"
/// assert_eq!(*map.find_or_insert("a", 1i), 1);
///
/// // Find the existing key
/// assert_eq!(*map.find_or_insert("a", -2), 1);
/// ```
pub fn find_or_insert<'a>(&'a mut self, k: K, v: V) -> &'a mut V {
self.find_with_or_insert_with(k, v, |_k, _v, _a| (), |_k, a| a)
}
/// Return the value corresponding to the key in the map, or create,
/// insert, and return a new value if it doesn't exist.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// let mut map = HashMap::new();
///
/// // Insert 10 with key 2
/// assert_eq!(*map.find_or_insert_with(2i, |&key| 5 * key as uint), 10u);
///
/// // Find the existing key
/// assert_eq!(*map.find_or_insert_with(2, |&key| key as uint), 10);
/// ```
pub fn find_or_insert_with<'a>(&'a mut self, k: K, f: |&K| -> V)
-> &'a mut V {
self.find_with_or_insert_with(k, (), |_k, _v, _a| (), |k, _a| f(k))
@ -1255,6 +1329,20 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// Insert a key-value pair into the map if the key is not already present.
/// Otherwise, modify the existing value for the key.
/// Returns the new or modified value for the key.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
/// let mut map = HashMap::new();
///
/// // Insert 2 with key "a"
/// assert_eq!(*map.insert_or_update_with("a", 2u, |_key, val| *val = 3), 2);
///
/// // Update and return the existing value
/// assert_eq!(*map.insert_or_update_with("a", 9, |_key, val| *val = 7), 7);
/// assert_eq!(map.get(&"a"), &7);
/// ```
pub fn insert_or_update_with<'a>(
&'a mut self,
k: K,
@ -1268,13 +1356,15 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// insert and return a new value if it doesn't exist.
///
/// This method allows for all insertion behaviours of a hashmap;
/// see methods like `insert`, `find_or_insert` and
/// `insert_or_update_with` for less general and more friendly
/// variations of this.
/// see methods like
/// [`insert`](../trait.MutableMap.html#tymethod.insert),
/// [`find_or_insert`](#method.find_or_insert) and
/// [`insert_or_update_with`](#method.insert_or_update_with)
/// for less general and more friendly variations of this.
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashMap;
///
/// // map some strings to vectors of strings
@ -1326,7 +1416,22 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
}
}
/// Retrieves a value for the given key, failing if the key is not present.
/// Retrieves a value for the given key.
/// See [`find`](../trait.Map.html#tymethod.find) for a non-failing alternative.
///
/// # Failure
///
/// Fails if the key is not present.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// assert_eq!(map.get(&"a"), &1);
/// ```
pub fn get<'a>(&'a self, k: &K) -> &'a V {
match self.find(k) {
Some(v) => v,
@ -1334,7 +1439,31 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
}
}
/// Retrieves a (mutable) value for the given key, failing if the key is not present.
/// Retrieves a mutable value for the given key.
/// See [`find_mut`](../trait.MutableMap.html#tymethod.find_mut) for a non-failing alternative.
///
/// # Failure
///
/// Fails if the key is not present.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// {
/// // val will freeze map to prevent usage during its lifetime
/// let val = map.get_mut(&"a");
/// *val = 40;
/// }
/// assert_eq!(map.get(&"a"), &40);
///
/// // A more direct way could be:
/// *map.get_mut(&"a") = -2;
/// assert_eq!(map.get(&"a"), &-2);
/// ```
pub fn get_mut<'a>(&'a mut self, k: &K) -> &'a mut V {
match self.find_mut(k) {
Some(v) => v,
@ -1344,12 +1473,16 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// Return true if the map contains a value for the specified key,
/// using equivalence.
///
/// See [pop_equiv](#method.pop_equiv) for an extended example.
pub fn contains_key_equiv<Q: Hash<S> + Equiv<K>>(&self, key: &Q) -> bool {
self.search_equiv(key).is_some()
}
/// Return the value corresponding to the key in the map, using
/// equivalence.
///
/// See [pop_equiv](#method.pop_equiv) for an extended example.
pub fn find_equiv<'a, Q: Hash<S> + Equiv<K>>(&'a self, k: &Q) -> Option<&'a V> {
match self.search_equiv(k) {
None => None,
@ -1360,27 +1493,154 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
}
}
/// Remove an equivalent key from the map, returning the value at the
/// key if the key was previously in the map.
///
/// # Example
///
/// This is a slightly silly example where we define the number's parity as
/// the equivalence class. It is important that the values hash the same,
/// which is why we override `Hash`.
///
/// ```
/// use std::collections::HashMap;
/// use std::hash::Hash;
/// use std::hash::sip::SipState;
///
/// #[deriving(Eq, PartialEq)]
/// struct EvenOrOdd {
/// num: uint
/// };
///
/// impl Hash for EvenOrOdd {
/// fn hash(&self, state: &mut SipState) {
/// let parity = self.num % 2;
/// parity.hash(state);
/// }
/// }
///
/// impl Equiv<EvenOrOdd> for EvenOrOdd {
/// fn equiv(&self, other: &EvenOrOdd) -> bool {
/// self.num % 2 == other.num % 2
/// }
/// }
///
/// let mut map = HashMap::new();
/// map.insert(EvenOrOdd { num: 3 }, "foo");
///
/// assert!(map.contains_key_equiv(&EvenOrOdd { num: 1 }));
/// assert!(!map.contains_key_equiv(&EvenOrOdd { num: 4 }));
///
/// assert_eq!(map.find_equiv(&EvenOrOdd { num: 5 }), Some(&"foo"));
/// assert_eq!(map.find_equiv(&EvenOrOdd { num: 2 }), None);
///
/// assert_eq!(map.pop_equiv(&EvenOrOdd { num: 1 }), Some("foo"));
/// assert_eq!(map.pop_equiv(&EvenOrOdd { num: 2 }), None);
///
/// ```
#[experimental]
pub fn pop_equiv<Q:Hash<S> + Equiv<K>>(&mut self, k: &Q) -> Option<V> {
if self.table.size() == 0 {
return None
}
let potential_new_size = self.table.size() - 1;
self.make_some_room(potential_new_size);
let starting_index = match self.search_equiv(k) {
Some(idx) => idx,
None => return None,
};
self.pop_internal(starting_index)
}
/// An iterator visiting all keys in arbitrary order.
/// Iterator element type is &'a K.
/// Iterator element type is `&'a K`.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// map.insert("b", 2);
/// map.insert("c", 3);
///
/// for key in map.keys() {
/// println!("{}", key);
/// }
/// ```
pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
self.iter().map(|(k, _v)| k)
}
/// An iterator visiting all values in arbitrary order.
/// Iterator element type is &'a V.
/// Iterator element type is `&'a V`.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// map.insert("b", 2);
/// map.insert("c", 3);
///
/// for key in map.values() {
/// println!("{}", key);
/// }
/// ```
pub fn values<'a>(&'a self) -> Values<'a, K, V> {
self.iter().map(|(_k, v)| v)
}
/// An iterator visiting all key-value pairs in arbitrary order.
/// Iterator element type is (&'a K, &'a V).
/// Iterator element type is `(&'a K, &'a V)`.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// map.insert("b", 2);
/// map.insert("c", 3);
///
/// for (key, val) in map.iter() {
/// println!("key: {} val: {}", key, val);
/// }
/// ```
pub fn iter<'a>(&'a self) -> Entries<'a, K, V> {
self.table.iter()
}
/// An iterator visiting all key-value pairs in arbitrary order,
/// with mutable references to the values.
/// Iterator element type is (&'a K, &'a mut V).
/// Iterator element type is `(&'a K, &'a mut V)`.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// map.insert("b", 2);
/// map.insert("c", 3);
///
/// // Update all values
/// for (_, val) in map.mut_iter() {
/// *val *= 2;
/// }
///
/// for (key, val) in map.iter() {
/// println!("key: {} val: {}", key, val);
/// }
/// ```
pub fn mut_iter<'a>(&'a mut self) -> MutEntries<'a, K, V> {
self.table.mut_iter()
}
@ -1388,18 +1648,56 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
/// Creates a consuming iterator, that is, one that moves each key-value
/// pair out of the map in arbitrary order. The map cannot be used after
/// calling this.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("a", 1i);
/// map.insert("b", 2);
/// map.insert("c", 3);
///
/// // Not possible with .iter()
/// let vec: Vec<(&str, int)> = map.move_iter().collect();
/// ```
pub fn move_iter(self) -> MoveEntries<K, V> {
self.table.move_iter().map(|(_, k, v)| (k, v))
}
}
impl<K: Eq + Hash<S>, V: Clone, S, H: Hasher<S>> HashMap<K, V, H> {
/// Like `find`, but returns a copy of the value.
/// Return a copy of the value corresponding to the key.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map: HashMap<uint, String> = HashMap::new();
/// map.insert(1u, "foo".to_string());
/// let s: String = map.find_copy(&1).unwrap();
/// ```
pub fn find_copy(&self, k: &K) -> Option<V> {
self.find(k).map(|v| (*v).clone())
}
/// Like `get`, but returns a copy of the value.
/// Return a copy of the value corresponding to the key.
///
/// # Failure
///
/// Fails if the key is not present.
///
/// # Example
///
/// ```
/// use std::collections::HashMap;
///
/// let mut map: HashMap<uint, String> = HashMap::new();
/// map.insert(1u, "foo".to_string());
/// let s: String = map.get_copy(&1);
/// ```
pub fn get_copy(&self, k: &K) -> V {
(*self.get(k)).clone()
}
@ -1489,7 +1787,7 @@ pub type SetMoveItems<K> =
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// // Type inference lets us omit an explicit type signature (which
@ -1552,7 +1850,6 @@ impl<T: Hash + Eq> HashSet<T, RandomSipHasher> {
///
/// # Example
///
/// ```rust
/// use std::collections::HashSet;
/// let mut set: HashSet<int> = HashSet::new();
/// ```
@ -1566,7 +1863,6 @@ impl<T: Hash + Eq> HashSet<T, RandomSipHasher> {
///
/// # Example
///
/// ```rust
/// use std::collections::HashSet;
/// let mut set: HashSet<int> = HashSet::with_capacity(10);
/// ```
@ -1624,7 +1920,6 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// use std::collections::HashSet;
/// let mut set: HashSet<int> = HashSet::new();
/// set.reserve(10);
@ -1683,9 +1978,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let mut set = HashSet::new();
/// set.insert("a");
/// set.insert("b");
@ -1705,9 +1999,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let mut set = HashSet::new();
/// set.insert("a".to_string());
/// set.insert("b".to_string());
@ -1728,9 +2021,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let a: HashSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
/// let b: HashSet<int> = [4i, 2, 3, 4].iter().map(|&x| x).collect();
///
@ -1758,9 +2050,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let a: HashSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
/// let b: HashSet<int> = [4i, 2, 3, 4].iter().map(|&x| x).collect();
///
@ -1784,9 +2075,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let a: HashSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
/// let b: HashSet<int> = [4i, 2, 3, 4].iter().map(|&x| x).collect();
///
@ -1810,9 +2100,8 @@ impl<T: Eq + Hash<S>, S, H: Hasher<S>> HashSet<T, H> {
///
/// # Example
///
/// ```rust
/// ```
/// use std::collections::HashSet;
///
/// let a: HashSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
/// let b: HashSet<int> = [4i, 2, 3, 4].iter().map(|&x| x).collect();
///