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matthiaskrgrmatthiaskrgr
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Rollup merge of #91482 - JosephTLyons:update-HashMap-and-BTreeMap-documentation, r=yaahc
Update documentation to use `from()` to initialize `HashMap`s and `BTreeMap`s As of Rust 1.56, `HashMap` and `BTreeMap` both have associated `from()` functions. I think using these in the documentation cleans things up a bit. It allows us to remove some of the `mut`s and avoids the Initialize-Then-Modify anti-pattern.
2 parents b7b4d77 + 72a6974 commit 5510803

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  • library
    • alloc/src/collections/btree
    • std/src/collections/hash

2 files changed

+75
-57
lines changed

‎library/alloc/src/collections/btree/map.rs‎

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -2107,10 +2107,11 @@ impl<K, V> BTreeMap<K, V> {
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/// ```
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/// use std::collections::BTreeMap;
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///
2110-
/// let mut map = BTreeMap::new();
2111-
/// map.insert("a", 1);
2112-
/// map.insert("b", 2);
2113-
/// map.insert("c", 3);
2110+
/// let mut map = BTreeMap::from([
2111+
/// ("a", 1),
2112+
/// ("b", 2),
2113+
/// ("c", 3),
2114+
/// ]);
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///
21152116
/// // add 10 to the value if the key isn't "a"
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/// for (key, value) in map.iter_mut() {

‎library/std/src/collections/hash/map.rs‎

Lines changed: 70 additions & 53 deletions
Original file line numberDiff line numberDiff line change
@@ -334,10 +334,11 @@ impl<K, V, S> HashMap<K, V, S> {
334334
/// ```
335335
/// use std::collections::HashMap;
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///
337-
/// let mut map = HashMap::new();
338-
/// map.insert("a", 1);
339-
/// map.insert("b", 2);
340-
/// map.insert("c", 3);
337+
/// let map = HashMap::from([
338+
/// ("a", 1),
339+
/// ("b", 2),
340+
/// ("c", 3),
341+
/// ]);
341342
///
342343
/// for key in map.keys() {
343344
/// println!("{}", key);
@@ -356,10 +357,11 @@ impl<K, V, S> HashMap<K, V, S> {
356357
/// ```
357358
/// use std::collections::HashMap;
358359
///
359-
/// let mut map = HashMap::new();
360-
/// map.insert("a", 1);
361-
/// map.insert("b", 2);
362-
/// map.insert("c", 3);
360+
/// let map = HashMap::from([
361+
/// ("a", 1),
362+
/// ("b", 2),
363+
/// ("c", 3),
364+
/// ]);
363365
///
364366
/// for val in map.values() {
365367
/// println!("{}", val);
@@ -378,11 +380,11 @@ impl<K, V, S> HashMap<K, V, S> {
378380
/// ```
379381
/// use std::collections::HashMap;
380382
///
381-
/// let mut map = HashMap::new();
382-
///
383-
/// map.insert("a", 1);
384-
/// map.insert("b", 2);
385-
/// map.insert("c", 3);
383+
/// let mut map = HashMap::from([
384+
/// ("a", 1),
385+
/// ("b", 2),
386+
/// ("c", 3),
387+
/// ]);
386388
///
387389
/// for val in map.values_mut() {
388390
/// *val = *val + 10;
@@ -405,10 +407,11 @@ impl<K, V, S> HashMap<K, V, S> {
405407
/// ```
406408
/// use std::collections::HashMap;
407409
///
408-
/// let mut map = HashMap::new();
409-
/// map.insert("a", 1);
410-
/// map.insert("b", 2);
411-
/// map.insert("c", 3);
410+
/// let map = HashMap::from([
411+
/// ("a", 1),
412+
/// ("b", 2),
413+
/// ("c", 3),
414+
/// ]);
412415
///
413416
/// for (key, val) in map.iter() {
414417
/// println!("key: {} val: {}", key, val);
@@ -428,10 +431,11 @@ impl<K, V, S> HashMap<K, V, S> {
428431
/// ```
429432
/// use std::collections::HashMap;
430433
///
431-
/// let mut map = HashMap::new();
432-
/// map.insert("a", 1);
433-
/// map.insert("b", 2);
434-
/// map.insert("c", 3);
434+
/// let mut map = HashMap::from([
435+
/// ("a", 1),
436+
/// ("b", 2),
437+
/// ("c", 3),
438+
/// ]);
435439
///
436440
/// // Update all values
437441
/// for (_, val) in map.iter_mut() {
@@ -966,10 +970,11 @@ where
966970
/// ```
967971
/// use std::collections::HashMap;
968972
///
969-
/// let mut map = HashMap::new();
970-
/// map.insert("a", 1);
971-
/// map.insert("b", 2);
972-
/// map.insert("c", 3);
973+
/// let map = HashMap::from([
974+
/// ("a", 1),
975+
/// ("b", 2),
976+
/// ("c", 3),
977+
/// ]);
973978
///
974979
/// let mut vec: Vec<&str> = map.into_keys().collect();
975980
/// // The `IntoKeys` iterator produces keys in arbitrary order, so the
@@ -992,10 +997,11 @@ where
992997
/// ```
993998
/// use std::collections::HashMap;
994999
///
995-
/// let mut map = HashMap::new();
996-
/// map.insert("a", 1);
997-
/// map.insert("b", 2);
998-
/// map.insert("c", 3);
1000+
/// let map = HashMap::from([
1001+
/// ("a", 1),
1002+
/// ("b", 2),
1003+
/// ("c", 3),
1004+
/// ]);
9991005
///
10001006
/// let mut vec: Vec<i32> = map.into_values().collect();
10011007
/// // The `IntoValues` iterator produces values in arbitrary order, so
@@ -1202,8 +1208,9 @@ where
12021208
/// ```
12031209
/// use std::collections::HashMap;
12041210
///
1205-
/// let mut map = HashMap::new();
1206-
/// map.insert("a", 1);
1211+
/// let map = HashMap::from([
1212+
/// ("a", 1),
1213+
/// ]);
12071214
/// let iter = map.iter();
12081215
/// ```
12091216
#[stable(feature = "rust1", since = "1.0.0")]
@@ -1239,8 +1246,9 @@ impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
12391246
/// ```
12401247
/// use std::collections::HashMap;
12411248
///
1242-
/// let mut map = HashMap::new();
1243-
/// map.insert("a", 1);
1249+
/// let mut map = HashMap::from([
1250+
/// ("a", 1),
1251+
/// ]);
12441252
/// let iter = map.iter_mut();
12451253
/// ```
12461254
#[stable(feature = "rust1", since = "1.0.0")]
@@ -1269,8 +1277,9 @@ impl<'a, K, V> IterMut<'a, K, V> {
12691277
/// ```
12701278
/// use std::collections::HashMap;
12711279
///
1272-
/// let mut map = HashMap::new();
1273-
/// map.insert("a", 1);
1280+
/// let map = HashMap::from([
1281+
/// ("a", 1),
1282+
/// ]);
12741283
/// let iter = map.into_iter();
12751284
/// ```
12761285
#[stable(feature = "rust1", since = "1.0.0")]
@@ -1298,8 +1307,9 @@ impl<K, V> IntoIter<K, V> {
12981307
/// ```
12991308
/// use std::collections::HashMap;
13001309
///
1301-
/// let mut map = HashMap::new();
1302-
/// map.insert("a", 1);
1310+
/// let map = HashMap::from([
1311+
/// ("a", 1),
1312+
/// ]);
13031313
/// let iter_keys = map.keys();
13041314
/// ```
13051315
#[stable(feature = "rust1", since = "1.0.0")]
@@ -1335,8 +1345,9 @@ impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
13351345
/// ```
13361346
/// use std::collections::HashMap;
13371347
///
1338-
/// let mut map = HashMap::new();
1339-
/// map.insert("a", 1);
1348+
/// let map = HashMap::from([
1349+
/// ("a", 1),
1350+
/// ]);
13401351
/// let iter_values = map.values();
13411352
/// ```
13421353
#[stable(feature = "rust1", since = "1.0.0")]
@@ -1372,8 +1383,9 @@ impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
13721383
/// ```
13731384
/// use std::collections::HashMap;
13741385
///
1375-
/// let mut map = HashMap::new();
1376-
/// map.insert("a", 1);
1386+
/// let mut map = HashMap::from([
1387+
/// ("a", 1),
1388+
/// ]);
13771389
/// let iter = map.drain();
13781390
/// ```
13791391
#[stable(feature = "drain", since = "1.6.0")]
@@ -1402,8 +1414,9 @@ impl<'a, K, V> Drain<'a, K, V> {
14021414
///
14031415
/// use std::collections::HashMap;
14041416
///
1405-
/// let mut map = HashMap::new();
1406-
/// map.insert("a", 1);
1417+
/// let mut map = HashMap::from([
1418+
/// ("a", 1),
1419+
/// ]);
14071420
/// let iter = map.drain_filter(|_k, v| *v % 2 == 0);
14081421
/// ```
14091422
#[unstable(feature = "hash_drain_filter", issue = "59618")]
@@ -1426,8 +1439,9 @@ where
14261439
/// ```
14271440
/// use std::collections::HashMap;
14281441
///
1429-
/// let mut map = HashMap::new();
1430-
/// map.insert("a", 1);
1442+
/// let mut map = HashMap::from([
1443+
/// ("a", 1),
1444+
/// ]);
14311445
/// let iter_values = map.values_mut();
14321446
/// ```
14331447
#[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1447,8 +1461,9 @@ pub struct ValuesMut<'a, K: 'a, V: 'a> {
14471461
/// ```
14481462
/// use std::collections::HashMap;
14491463
///
1450-
/// let mut map = HashMap::new();
1451-
/// map.insert("a", 1);
1464+
/// let map = HashMap::from([
1465+
/// ("a", 1),
1466+
/// ]);
14521467
/// let iter_keys = map.into_keys();
14531468
/// ```
14541469
#[stable(feature = "map_into_keys_values", since = "1.54.0")]
@@ -1468,8 +1483,9 @@ pub struct IntoKeys<K, V> {
14681483
/// ```
14691484
/// use std::collections::HashMap;
14701485
///
1471-
/// let mut map = HashMap::new();
1472-
/// map.insert("a", 1);
1486+
/// let map = HashMap::from([
1487+
/// ("a", 1),
1488+
/// ]);
14731489
/// let iter_keys = map.into_values();
14741490
/// ```
14751491
#[stable(feature = "map_into_keys_values", since = "1.54.0")]
@@ -2004,10 +2020,11 @@ impl<K, V, S> IntoIterator for HashMap<K, V, S> {
20042020
/// ```
20052021
/// use std::collections::HashMap;
20062022
///
2007-
/// let mut map = HashMap::new();
2008-
/// map.insert("a", 1);
2009-
/// map.insert("b", 2);
2010-
/// map.insert("c", 3);
2023+
/// let map = HashMap::from([
2024+
/// ("a", 1),
2025+
/// ("b", 2),
2026+
/// ("c", 3),
2027+
/// ]);
20112028
///
20122029
/// // Not possible with .iter()
20132030
/// let vec: Vec<(&str, i32)> = map.into_iter().collect();

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