Struct std::collections::VecMapUnstable
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pub struct VecMap<V> {
// some fields omitted
}A map optimized for small integer keys.
Examples
fn main() { use std::collections::VecMap; let mut months = VecMap::new(); months.insert(1, "Jan"); months.insert(2, "Feb"); months.insert(3, "Mar"); if !months.contains_key(&12) { println!("The end is near!"); } assert_eq!(months.get(&1), Some(&"Jan")); match months.get_mut(&3) { Some(value) => *value = "Venus", None => (), } assert_eq!(months.get(&3), Some(&"Venus")); // Print out all months for (key, value) in months.iter() { println!("month {} is {}", key, value); } months.clear(); assert!(months.is_empty()); }use std::collections::VecMap; let mut months = VecMap::new(); months.insert(1, "Jan"); months.insert(2, "Feb"); months.insert(3, "Mar"); if !months.contains_key(&12) { println!("The end is near!"); } assert_eq!(months.get(&1), Some(&"Jan")); match months.get_mut(&3) { Some(value) => *value = "Venus", None => (), } assert_eq!(months.get(&3), Some(&"Venus")); // Print out all months for (key, value) in months.iter() { println!("month {} is {}", key, value); } months.clear(); assert!(months.is_empty());
Methods
impl<V> VecMap<V>
fn new() -> VecMap<V>
Creates an empty VecMap.
Examples
fn main() { use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new(); }use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new();
fn with_capacity(capacity: usize) -> VecMap<V>
Creates an empty VecMap with space for at least capacity
elements before resizing.
Examples
fn main() { use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::with_capacity(10); }use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::with_capacity(10);
fn capacity(&self) -> usize
Returns the number of elements the VecMap can hold without
reallocating.
Examples
fn main() { use std::collections::VecMap; let map: VecMap<String> = VecMap::with_capacity(10); assert!(map.capacity() >= 10); }use std::collections::VecMap; let map: VecMap<String> = VecMap::with_capacity(10); assert!(map.capacity() >= 10);
fn reserve_len(&mut self, len: usize)
Reserves capacity for the given VecMap to contain len distinct keys.
In the case of VecMap this means reallocations will not occur as long
as all inserted keys are less than len.
The collection may reserve more space to avoid frequent reallocations.
Examples
fn main() { use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new(); map.reserve_len(10); assert!(map.capacity() >= 10); }use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new(); map.reserve_len(10); assert!(map.capacity() >= 10);
fn reserve_len_exact(&mut self, len: usize)
Reserves the minimum capacity for the given VecMap to contain len distinct keys.
In the case of VecMap this means reallocations will not occur as long as all inserted
keys are less than len.
Note that the allocator may give the collection more space than it requests.
Therefore capacity cannot be relied upon to be precisely minimal. Prefer
reserve_len if future insertions are expected.
Examples
fn main() { use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new(); map.reserve_len_exact(10); assert!(map.capacity() >= 10); }use std::collections::VecMap; let mut map: VecMap<&str> = VecMap::new(); map.reserve_len_exact(10); assert!(map.capacity() >= 10);
fn keys(&'r self) -> Keys<'r, V>
Returns an iterator visiting all keys in ascending order of the keys.
The iterator's element type is usize.
fn values(&'r self) -> Values<'r, V>
Returns an iterator visiting all values in ascending order of the keys.
The iterator's element type is &'r V.
fn iter(&'r self) -> Iter<'r, V>
Returns an iterator visiting all key-value pairs in ascending order of the keys.
The iterator's element type is (usize, &'r V).
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); // Print `1: a` then `2: b` then `3: c` for (key, value) in map.iter() { println!("{}: {}", key, value); } }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); // Print `1: a` then `2: b` then `3: c` for (key, value) in map.iter() { println!("{}: {}", key, value); }
fn iter_mut(&'r mut self) -> IterMut<'r, V>
Returns an iterator visiting all key-value pairs in ascending order of the keys,
with mutable references to the values.
The iterator's element type is (usize, &'r mut V).
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(2, "b"); map.insert(3, "c"); for (key, value) in map.iter_mut() { *value = "x"; } for (key, value) in map.iter() { assert_eq!(value, &"x"); } }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(2, "b"); map.insert(3, "c"); for (key, value) in map.iter_mut() { *value = "x"; } for (key, value) in map.iter() { assert_eq!(value, &"x"); }
fn into_iter(self) -> IntoIter<V>
Returns an iterator visiting all key-value pairs in ascending order of
the keys, consuming the original VecMap.
The iterator's element type is (usize, &'r V).
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); let vec: Vec<(usize, &str)> = map.into_iter().collect(); assert_eq!(vec, vec![(1, "a"), (2, "b"), (3, "c")]); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); let vec: Vec<(usize, &str)> = map.into_iter().collect(); assert_eq!(vec, vec![(1, "a"), (2, "b"), (3, "c")]);
fn drain(&'a mut self) -> Drain<'a, V>
Returns an iterator visiting all key-value pairs in ascending order of
the keys, emptying (but not consuming) the original VecMap.
The iterator's element type is (usize, &'r V). Keeps the allocated memory for reuse.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); let vec: Vec<(usize, &str)> = map.drain().collect(); assert_eq!(vec, vec![(1, "a"), (2, "b"), (3, "c")]); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); map.insert(3, "c"); map.insert(2, "b"); let vec: Vec<(usize, &str)> = map.drain().collect(); assert_eq!(vec, vec![(1, "a"), (2, "b"), (3, "c")]);
fn len(&self) -> usize
Return the number of elements in the map.
Examples
fn main() { use std::collections::VecMap; let mut a = VecMap::new(); assert_eq!(a.len(), 0); a.insert(1, "a"); assert_eq!(a.len(), 1); }use std::collections::VecMap; let mut a = VecMap::new(); assert_eq!(a.len(), 0); a.insert(1, "a"); assert_eq!(a.len(), 1);
fn is_empty(&self) -> bool
Return true if the map contains no elements.
Examples
fn main() { use std::collections::VecMap; let mut a = VecMap::new(); assert!(a.is_empty()); a.insert(1, "a"); assert!(!a.is_empty()); }use std::collections::VecMap; let mut a = VecMap::new(); assert!(a.is_empty()); a.insert(1, "a"); assert!(!a.is_empty());
fn clear(&mut self)
Clears the map, removing all key-value pairs.
Examples
fn main() { use std::collections::VecMap; let mut a = VecMap::new(); a.insert(1, "a"); a.clear(); assert!(a.is_empty()); }use std::collections::VecMap; let mut a = VecMap::new(); a.insert(1, "a"); a.clear(); assert!(a.is_empty());
fn get(&self, key: &usize) -> Option<&V>
Returns a reference to the value corresponding to the key.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.get(&1), Some(&"a")); assert_eq!(map.get(&2), None); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.get(&1), Some(&"a")); assert_eq!(map.get(&2), None);
fn contains_key(&self, key: &usize) -> bool
Returns true if the map contains a value for the specified key.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.contains_key(&1), true); assert_eq!(map.contains_key(&2), false); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.contains_key(&1), true); assert_eq!(map.contains_key(&2), false);
fn get_mut(&mut self, key: &usize) -> Option<&mut V>
Returns a mutable reference to the value corresponding to the key.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); match map.get_mut(&1) { Some(x) => *x = "b", None => (), } assert_eq!(map[1], "b"); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); match map.get_mut(&1) { Some(x) => *x = "b", None => (), } assert_eq!(map[1], "b");
fn insert(&mut self, key: usize, value: V) -> Option<V>
Inserts a key-value pair from the map. If the key already had a value
present in the map, that value is returned. Otherwise, None is returned.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); assert_eq!(map.insert(37, "a"), None); assert_eq!(map.is_empty(), false); map.insert(37, "b"); assert_eq!(map.insert(37, "c"), Some("b")); assert_eq!(map[37], "c"); }use std::collections::VecMap; let mut map = VecMap::new(); assert_eq!(map.insert(37, "a"), None); assert_eq!(map.is_empty(), false); map.insert(37, "b"); assert_eq!(map.insert(37, "c"), Some("b")); assert_eq!(map[37], "c");
fn remove(&mut self, key: &usize) -> Option<V>
Removes a key from the map, returning the value at the key if the key was previously in the map.
Examples
fn main() { use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.remove(&1), Some("a")); assert_eq!(map.remove(&1), None); }use std::collections::VecMap; let mut map = VecMap::new(); map.insert(1, "a"); assert_eq!(map.remove(&1), Some("a")); assert_eq!(map.remove(&1), None);
fn entry(&mut self, key: usize) -> Entry<V>
Gets the given key's corresponding entry in the map for in-place manipulation.
Examples
fn main() { use std::collections::VecMap; use std::collections::vec_map::Entry; let mut count: VecMap<u32> = VecMap::new(); // count the number of occurrences of numbers in the vec for x in vec![1, 2, 1, 2, 3, 4, 1, 2, 4].iter() { match count.entry(*x) { Entry::Vacant(view) => { view.insert(1); }, Entry::Occupied(mut view) => { let v = view.get_mut(); *v += 1; }, } } assert_eq!(count[1], 3); }use std::collections::VecMap; use std::collections::vec_map::Entry; let mut count: VecMap<u32> = VecMap::new(); // count the number of occurrences of numbers in the vec for x in vec![1, 2, 1, 2, 3, 4, 1, 2, 4].iter() { match count.entry(*x) { Entry::Vacant(view) => { view.insert(1); }, Entry::Occupied(mut view) => { let v = view.get_mut(); *v += 1; }, } } assert_eq!(count[1], 3);