/
map.ex
900 lines (673 loc) · 22.2 KB
/
map.ex
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
defmodule Map do
@moduledoc """
A set of functions for working with maps.
Many functions for maps, which implement the `Enumerable` protocol,
are found in the `Enum` module. Additionally, the following functions
for maps are found in `Kernel`:
* `map_size/1`
Maps are the "go to" key-value data structure in Elixir. Maps can be created
with the `%{}` syntax, and key-value pairs can be expressed as `key => value`:
iex> %{}
%{}
iex> %{"one" => :two, 3 => "four"}
%{3 => "four", "one" => :two}
Key-value pairs in a map do not follow any order (that's why the printed map
in the example above has a different order than the map that was created).
Maps do not impose any restriction on the key type: anything can be a key in a
map. As a key-value structure, maps do not allow duplicated keys. Keys are
compared using the exact-equality operator (`===/2`). If colliding keys are defined
in a map literal, the last one prevails.
When the key in a key-value pair is an atom, the `key: value` shorthand syntax
can be used (as in many other special forms), provided key-value pairs are put at
the end:
iex> %{"hello" => "world", a: 1, b: 2}
%{:a => 1, :b => 2, "hello" => "world"}
Keys in maps can be accessed through some of the functions in this module
(such as `Map.get/3` or `Map.fetch/2`) or through the `map[]` syntax provided
by the `Access` module:
iex> map = %{a: 1, b: 2}
iex> Map.fetch(map, :a)
{:ok, 1}
iex> map[:b]
2
iex> map["non_existing_key"]
nil
For accessing atom keys, one may also `map.key`. Note that while `map[key]` will
return `nil` if `map` doesn't contain `key`, `map.key` will raise if `map` doesn't
contain the key `:key`.
iex> map = %{foo: "bar", baz: "bong"}
iex> map.foo
"bar"
iex> map.non_existing_key
** (KeyError) key :non_existing_key not found in: %{baz: "bong", foo: "bar"}
The two syntaxes for accessing keys reveal the dual nature of maps. The `map[key]`
syntax is used for dynamically created maps that may have any key, of any type.
`map.key` is used with maps that hold a predetermined set of atoms keys, which are
expected to always be present. Structs, defined via `defstruct/1`, are one example
of such "static maps", where the keys can also be checked during compile time.
Maps can be pattern matched on. When a map is on the left-hand side of a
pattern match, it will match if the map on the right-hand side contains the
keys on the left-hand side and their values match the ones on the left-hand
side. This means that an empty map matches every map.
iex> %{} = %{foo: "bar"}
%{foo: "bar"}
iex> %{a: a} = %{:a => 1, "b" => 2, [:c, :e, :e] => 3}
iex> a
1
iex> %{:c => 3} = %{:a => 1, 2 => :b}
** (MatchError) no match of right hand side value: %{2 => :b, :a => 1}
Variables can be used as map keys both when writing map literals as well as
when matching:
iex> n = 1
1
iex> %{n => :one}
%{1 => :one}
iex> %{^n => :one} = %{1 => :one, 2 => :two, 3 => :three}
%{1 => :one, 2 => :two, 3 => :three}
Maps also support a specific update syntax to update the value stored under
*existing* atom keys:
iex> map = %{one: 1, two: 2}
iex> %{map | one: "one"}
%{one: "one", two: 2}
iex> %{map | three: 3}
** (KeyError) key :three not found
"""
@type key :: any
@type value :: any
@compile {:inline, fetch: 2, fetch!: 2, get: 2, put: 3, delete: 2, has_key?: 2, replace!: 3}
@doc """
Returns all keys from `map`.
Inlined by the compiler.
## Examples
iex> Map.keys(%{a: 1, b: 2})
[:a, :b]
"""
@spec keys(map) :: [key]
defdelegate keys(map), to: :maps
@doc """
Returns all values from `map`.
Inlined by the compiler.
## Examples
iex> Map.values(%{a: 1, b: 2})
[1, 2]
"""
@spec values(map) :: [value]
defdelegate values(map), to: :maps
@doc """
Converts `map` to a list.
Each key-value pair in the map is converted to a two-element tuple `{key,
value}` in the resulting list.
Inlined by the compiler.
## Examples
iex> Map.to_list(%{a: 1})
[a: 1]
iex> Map.to_list(%{1 => 2})
[{1, 2}]
"""
@spec to_list(map) :: [{term, term}]
defdelegate to_list(map), to: :maps
@doc """
Returns a new empty map.
## Examples
iex> Map.new()
%{}
"""
@spec new :: map
def new, do: %{}
@doc """
Creates a map from an `enumerable`.
Duplicated keys are removed; the latest one prevails.
## Examples
iex> Map.new([{:b, 1}, {:a, 2}])
%{a: 2, b: 1}
iex> Map.new([a: 1, a: 2, a: 3])
%{a: 3}
"""
@spec new(Enumerable.t()) :: map
def new(enumerable)
def new(list) when is_list(list), do: :maps.from_list(list)
def new(%_{} = struct), do: new_from_enum(struct)
def new(%{} = map), do: map
def new(enum), do: new_from_enum(enum)
defp new_from_enum(enumerable) do
enumerable
|> Enum.to_list()
|> :maps.from_list()
end
@doc """
Creates a map from an `enumerable` via the given transformation function.
Duplicated keys are removed; the latest one prevails.
## Examples
iex> Map.new([:a, :b], fn x -> {x, x} end)
%{a: :a, b: :b}
"""
@spec new(Enumerable.t(), (term -> {key, value})) :: map
def new(enumerable, transform) when is_function(transform, 1) do
enumerable
|> Enum.to_list()
|> new_transform(transform, [])
end
defp new_transform([], _fun, acc) do
acc
|> :lists.reverse()
|> :maps.from_list()
end
defp new_transform([item | rest], fun, acc) do
new_transform(rest, fun, [fun.(item) | acc])
end
@doc """
Returns whether the given `key` exists in the given `map`.
Inlined by the compiler.
## Examples
iex> Map.has_key?(%{a: 1}, :a)
true
iex> Map.has_key?(%{a: 1}, :b)
false
"""
@spec has_key?(map, key) :: boolean
def has_key?(map, key), do: :maps.is_key(key, map)
@doc """
Fetches the value for a specific `key` in the given `map`.
If `map` contains the given `key` with value `value`, then `{:ok, value}` is
returned. If `map` doesn't contain `key`, `:error` is returned.
Inlined by the compiler.
## Examples
iex> Map.fetch(%{a: 1}, :a)
{:ok, 1}
iex> Map.fetch(%{a: 1}, :b)
:error
"""
@spec fetch(map, key) :: {:ok, value} | :error
def fetch(map, key), do: :maps.find(key, map)
@doc """
Fetches the value for a specific `key` in the given `map`, erroring out if
`map` doesn't contain `key`.
If `map` contains the given `key`, the corresponding value is returned. If
`map` doesn't contain `key`, a `KeyError` exception is raised.
Inlined by the compiler.
## Examples
iex> Map.fetch!(%{a: 1}, :a)
1
iex> Map.fetch!(%{a: 1}, :b)
** (KeyError) key :b not found in: %{a: 1}
"""
@spec fetch!(map, key) :: value | no_return
def fetch!(map, key) do
:maps.get(key, map)
end
@doc """
Puts the given `value` under `key` unless the entry `key`
already exists in `map`.
## Examples
iex> Map.put_new(%{a: 1}, :b, 2)
%{a: 1, b: 2}
iex> Map.put_new(%{a: 1, b: 2}, :a, 3)
%{a: 1, b: 2}
"""
@spec put_new(map, key, value) :: map
def put_new(map, key, value) do
case map do
%{^key => _value} ->
map
%{} ->
put(map, key, value)
other ->
:erlang.error({:badmap, other})
end
end
@doc false
@deprecated "Use Map.fetch/2 + Map.put/3 instead"
def replace(map, key, value) do
case map do
%{^key => _value} ->
put(map, key, value)
%{} ->
map
other ->
:erlang.error({:badmap, other})
end
end
@doc """
Alters the value stored under `key` to `value`, but only
if the entry `key` already exists in `map`.
If `key` is not present in `map`, a `KeyError` exception is raised.
Inlined by the compiler.
## Examples
iex> Map.replace!(%{a: 1, b: 2}, :a, 3)
%{a: 3, b: 2}
iex> Map.replace!(%{a: 1}, :b, 2)
** (KeyError) key :b not found in: %{a: 1}
"""
@doc since: "1.5.0"
@spec replace!(map, key, value) :: map
def replace!(map, key, value) do
:maps.update(key, value, map)
end
@doc """
Evaluates `fun` and puts the result under `key`
in `map` unless `key` is already present.
This function is useful in case you want to compute the value to put under
`key` only if `key` is not already present (e.g., the value is expensive to
calculate or generally difficult to setup and teardown again).
## Examples
iex> map = %{a: 1}
iex> fun = fn ->
...> # some expensive operation here
...> 3
...> end
iex> Map.put_new_lazy(map, :a, fun)
%{a: 1}
iex> Map.put_new_lazy(map, :b, fun)
%{a: 1, b: 3}
"""
@spec put_new_lazy(map, key, (() -> value)) :: map
def put_new_lazy(map, key, fun) when is_function(fun, 0) do
case map do
%{^key => _value} ->
map
%{} ->
put(map, key, fun.())
other ->
:erlang.error({:badmap, other})
end
end
@doc """
Returns a new map with all the key-value pairs in `map` where the key
is in `keys`.
If `keys` contains keys that are not in `map`, they're simply ignored.
## Examples
iex> Map.take(%{a: 1, b: 2, c: 3}, [:a, :c, :e])
%{a: 1, c: 3}
"""
@spec take(map, Enumerable.t()) :: map
def take(map, keys)
def take(map, keys) when is_map(map) do
keys
|> Enum.to_list()
|> take(map, [])
end
def take(non_map, _keys) do
:erlang.error({:badmap, non_map})
end
defp take([], _map, acc) do
:maps.from_list(acc)
end
defp take([key | rest], map, acc) do
acc =
case map do
%{^key => value} -> [{key, value} | acc]
%{} -> acc
end
take(rest, map, acc)
end
@doc """
Gets the value for a specific `key` in `map`.
If `key` is present in `map` with value `value`, then `value` is
returned. Otherwise, `default` is returned (which is `nil` unless
specified otherwise).
## Examples
iex> Map.get(%{}, :a)
nil
iex> Map.get(%{a: 1}, :a)
1
iex> Map.get(%{a: 1}, :b)
nil
iex> Map.get(%{a: 1}, :b, 3)
3
"""
@spec get(map, key, value) :: value
def get(map, key, default \\ nil) do
case map do
%{^key => value} ->
value
%{} ->
default
other ->
:erlang.error({:badmap, other}, [map, key, default])
end
end
@doc """
Gets the value for a specific `key` in `map`.
If `key` is present in `map` with value `value`, then `value` is
returned. Otherwise, `fun` is evaluated and its result is returned.
This is useful if the default value is very expensive to calculate or
generally difficult to setup and teardown again.
## Examples
iex> map = %{a: 1}
iex> fun = fn ->
...> # some expensive operation here
...> 13
...> end
iex> Map.get_lazy(map, :a, fun)
1
iex> Map.get_lazy(map, :b, fun)
13
"""
@spec get_lazy(map, key, (() -> value)) :: value
def get_lazy(map, key, fun) when is_function(fun, 0) do
case map do
%{^key => value} ->
value
%{} ->
fun.()
other ->
:erlang.error({:badmap, other}, [map, key, fun])
end
end
@doc """
Puts the given `value` under `key` in `map`.
Inlined by the compiler.
## Examples
iex> Map.put(%{a: 1}, :b, 2)
%{a: 1, b: 2}
iex> Map.put(%{a: 1, b: 2}, :a, 3)
%{a: 3, b: 2}
"""
@spec put(map, key, value) :: map
def put(map, key, value) do
:maps.put(key, value, map)
end
@doc """
Deletes the entry in `map` for a specific `key`.
If the `key` does not exist, returns `map` unchanged.
Inlined by the compiler.
## Examples
iex> Map.delete(%{a: 1, b: 2}, :a)
%{b: 2}
iex> Map.delete(%{b: 2}, :a)
%{b: 2}
"""
@spec delete(map, key) :: map
def delete(map, key), do: :maps.remove(key, map)
@doc """
Merges two maps into one.
All keys in `map2` will be added to `map1`, overriding any existing one
(i.e., the keys in `map2` "have precedence" over the ones in `map1`).
If you have a struct and you would like to merge a set of keys into the
struct, do not use this function, as it would merge all keys on the right
side into the struct, even if the key is not part of the struct. Instead,
use `Kernel.struct/2`.
Inlined by the compiler.
## Examples
iex> Map.merge(%{a: 1, b: 2}, %{a: 3, d: 4})
%{a: 3, b: 2, d: 4}
"""
@spec merge(map, map) :: map
defdelegate merge(map1, map2), to: :maps
@doc """
Merges two maps into one, resolving conflicts through the given `fun`.
All keys in `map2` will be added to `map1`. The given function will be invoked
when there are duplicate keys; its arguments are `key` (the duplicate key),
`value1` (the value of `key` in `map1`), and `value2` (the value of `key` in
`map2`). The value returned by `fun` is used as the value under `key` in
the resulting map.
## Examples
iex> Map.merge(%{a: 1, b: 2}, %{a: 3, d: 4}, fn _k, v1, v2 ->
...> v1 + v2
...> end)
%{a: 4, b: 2, d: 4}
"""
@spec merge(map, map, (key, value, value -> value)) :: map
def merge(map1, map2, fun) when is_function(fun, 3) do
if map_size(map1) > map_size(map2) do
folder = fn key, val2, acc ->
update(acc, key, val2, fn val1 -> fun.(key, val1, val2) end)
end
:maps.fold(folder, map1, map2)
else
folder = fn key, val2, acc ->
update(acc, key, val2, fn val1 -> fun.(key, val2, val1) end)
end
:maps.fold(folder, map2, map1)
end
end
@doc """
Updates the `key` in `map` with the given function.
If `key` is present in `map` with value `value`, `fun` is invoked with
argument `value` and its result is used as the new value of `key`. If `key` is
not present in `map`, `initial` is inserted as the value of `key`. The initial
value will not be passed through the update function.
## Examples
iex> Map.update(%{a: 1}, :a, 13, &(&1 * 2))
%{a: 2}
iex> Map.update(%{a: 1}, :b, 11, &(&1 * 2))
%{a: 1, b: 11}
"""
@spec update(map, key, value, (value -> value)) :: map
def update(map, key, initial, fun) when is_function(fun, 1) do
case map do
%{^key => value} ->
put(map, key, fun.(value))
%{} ->
put(map, key, initial)
other ->
:erlang.error({:badmap, other}, [map, key, initial, fun])
end
end
@doc """
Returns and removes the value associated with `key` in `map`.
If `key` is present in `map` with value `value`, `{value, new_map}` is
returned where `new_map` is the result of removing `key` from `map`. If `key`
is not present in `map`, `{default, map}` is returned.
## Examples
iex> Map.pop(%{a: 1}, :a)
{1, %{}}
iex> Map.pop(%{a: 1}, :b)
{nil, %{a: 1}}
iex> Map.pop(%{a: 1}, :b, 3)
{3, %{a: 1}}
"""
@spec pop(map, key, value) :: {value, map}
def pop(map, key, default \\ nil) do
case :maps.take(key, map) do
{_, _} = tuple -> tuple
:error -> {default, map}
end
end
@doc """
Lazily returns and removes the value associated with `key` in `map`.
If `key` is present in `map` with value `value`, `{value, new_map}` is
returned where `new_map` is the result of removing `key` from `map`. If `key`
is not present in `map`, `{fun_result, map}` is returned, where `fun_result`
is the result of applying `fun`.
This is useful if the default value is very expensive to calculate or
generally difficult to setup and teardown again.
## Examples
iex> map = %{a: 1}
iex> fun = fn ->
...> # some expensive operation here
...> 13
...> end
iex> Map.pop_lazy(map, :a, fun)
{1, %{}}
iex> Map.pop_lazy(map, :b, fun)
{13, %{a: 1}}
"""
@spec pop_lazy(map, key, (() -> value)) :: {value, map}
def pop_lazy(map, key, fun) when is_function(fun, 0) do
case map do
%{^key => value} ->
{value, delete(map, key)}
%{} ->
{fun.(), map}
other ->
:erlang.error({:badmap, other}, [map, key, fun])
end
end
@doc """
Drops the given `keys` from `map`.
If `keys` contains keys that are not in `map`, they're simply ignored.
## Examples
iex> Map.drop(%{a: 1, b: 2, c: 3}, [:b, :d])
%{a: 1, c: 3}
"""
@spec drop(map, Enumerable.t()) :: map
def drop(map, keys)
def drop(map, keys) when is_map(map) do
keys
|> Enum.to_list()
|> drop_list(map)
end
def drop(non_map, keys) do
:erlang.error({:badmap, non_map}, [non_map, keys])
end
defp drop_list([], acc), do: acc
defp drop_list([key | rest], acc) do
drop_list(rest, delete(acc, key))
end
@doc """
Takes all entries corresponding to the given `keys` in `map` and extracts
them into a separate map.
Returns a tuple with the new map and the old map with removed keys.
Keys for which there are no entries in `map` are ignored.
## Examples
iex> Map.split(%{a: 1, b: 2, c: 3}, [:a, :c, :e])
{%{a: 1, c: 3}, %{b: 2}}
"""
@spec split(map, Enumerable.t()) :: {map, map}
def split(map, keys)
def split(map, keys) when is_map(map) do
keys
|> Enum.to_list()
|> split([], map)
end
def split(non_map, keys) do
:erlang.error({:badmap, non_map}, [non_map, keys])
end
defp split([], included, excluded) do
{:maps.from_list(included), excluded}
end
defp split([key | rest], included, excluded) do
case excluded do
%{^key => value} ->
split(rest, [{key, value} | included], delete(excluded, key))
_other ->
split(rest, included, excluded)
end
end
@doc """
Updates `key` with the given function.
If `key` is present in `map` with value `value`, `fun` is invoked with
argument `value` and its result is used as the new value of `key`. If `key` is
not present in `map`, a `KeyError` exception is raised.
## Examples
iex> Map.update!(%{a: 1}, :a, &(&1 * 2))
%{a: 2}
iex> Map.update!(%{a: 1}, :b, &(&1 * 2))
** (KeyError) key :b not found in: %{a: 1}
"""
@spec update!(map, key, (value -> value)) :: map
def update!(map, key, fun) when is_function(fun, 1) do
value = fetch!(map, key)
put(map, key, fun.(value))
end
@doc """
Gets the value from `key` and updates it, all in one pass.
`fun` is called with the current value under `key` in `map` (or `nil` if `key`
is not present in `map`) and must return a two-element tuple: the "get" value
(the retrieved value, which can be operated on before being returned) and the
new value to be stored under `key` in the resulting new map. `fun` may also
return `:pop`, which means the current value shall be removed from `map` and
returned (making this function behave like `Map.pop(map, key)`).
The returned value is a tuple with the "get" value returned by
`fun` and a new map with the updated value under `key`.
## Examples
iex> Map.get_and_update(%{a: 1}, :a, fn current_value ->
...> {current_value, "new value!"}
...> end)
{1, %{a: "new value!"}}
iex> Map.get_and_update(%{a: 1}, :b, fn current_value ->
...> {current_value, "new value!"}
...> end)
{nil, %{b: "new value!", a: 1}}
iex> Map.get_and_update(%{a: 1}, :a, fn _ -> :pop end)
{1, %{}}
iex> Map.get_and_update(%{a: 1}, :b, fn _ -> :pop end)
{nil, %{a: 1}}
"""
@spec get_and_update(map, key, (value -> {get, value} | :pop)) :: {get, map} when get: term
def get_and_update(map, key, fun) when is_function(fun, 1) do
current = get(map, key)
case fun.(current) do
{get, update} ->
{get, put(map, key, update)}
:pop ->
{current, delete(map, key)}
other ->
raise "the given function must return a two-element tuple or :pop, got: #{inspect(other)}"
end
end
@doc """
Gets the value from `key` and updates it. Raises if there is no `key`.
Behaves exactly like `get_and_update/3`, but raises a `KeyError` exception if
`key` is not present in `map`.
## Examples
iex> Map.get_and_update!(%{a: 1}, :a, fn current_value ->
...> {current_value, "new value!"}
...> end)
{1, %{a: "new value!"}}
iex> Map.get_and_update!(%{a: 1}, :b, fn current_value ->
...> {current_value, "new value!"}
...> end)
** (KeyError) key :b not found in: %{a: 1}
iex> Map.get_and_update!(%{a: 1}, :a, fn _ ->
...> :pop
...> end)
{1, %{}}
"""
@spec get_and_update!(map, key, (value -> {get, value} | :pop)) :: {get, map} | no_return
when get: term
def get_and_update!(map, key, fun) when is_function(fun, 1) do
value = fetch!(map, key)
case fun.(value) do
{get, update} ->
{get, put(map, key, update)}
:pop ->
{value, delete(map, key)}
other ->
raise "the given function must return a two-element tuple or :pop, got: #{inspect(other)}"
end
end
@doc """
Converts a `struct` to map.
It accepts the struct module or a struct itself and
simply removes the `__struct__` field from the given struct
or from a new struct generated from the given module.
## Example
defmodule User do
defstruct [:name]
end
Map.from_struct(User)
#=> %{name: nil}
Map.from_struct(%User{name: "john"})
#=> %{name: "john"}
"""
@spec from_struct(atom | struct) :: map
def from_struct(struct) when is_atom(struct) do
delete(struct.__struct__(), :__struct__)
end
def from_struct(%_{} = struct) do
delete(struct, :__struct__)
end
@doc """
Checks if two maps are equal.
Two maps are considered to be equal if they contain
the same keys and those keys contain the same values.
## Examples
iex> Map.equal?(%{a: 1, b: 2}, %{b: 2, a: 1})
true
iex> Map.equal?(%{a: 1, b: 2}, %{b: 1, a: 2})
false
"""
@spec equal?(map, map) :: boolean
def equal?(map1, map2)
def equal?(%{} = map1, %{} = map2), do: map1 === map2
def equal?(%{} = map1, map2), do: :erlang.error({:badmap, map2}, [map1, map2])
def equal?(term, other), do: :erlang.error({:badmap, term}, [term, other])
@doc false
# TODO: Remove on 2.0
@deprecated "Use Kernel.map_size/1 instead"
def size(map) do
map_size(map)
end
end