-
Notifications
You must be signed in to change notification settings - Fork 3.3k
/
keyword.ex
1065 lines (812 loc) · 28.3 KB
/
keyword.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
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
defmodule Keyword do
@moduledoc """
A set of functions for working with keywords.
A keyword list is a list of two-element tuples where the first
element of the tuple is an atom and the second element
can be any value.
For example, the following is a keyword list:
[{:exit_on_close, true}, {:active, :once}, {:packet_size, 1024}]
Elixir provides a special and more concise syntax for keyword lists
that looks like this:
[exit_on_close: true, active: :once, packet_size: 1024]
This is also the syntax that Elixir uses to inspect keyword lists:
iex> [{:active, :once}]
[active: :once]
The two syntaxes are completely equivalent. Like atoms, keywords
must be composed of Unicode characters such as letters, numbers,
underscore, and `@`. If the keyword has a character that does not
belong to the category above, such as spaces, you can wrap it in
quotes:
iex> ["exit on close": true]
["exit on close": true]
Wrapping a keyword in quotes does not make it a string. Keywords are
always atoms. If you use quotes when all characters are a valid part
of a keyword without quotes, Elixir will warn.
Note that when keyword lists are passed as the last argument to a function,
if the short-hand syntax is used then the square brackets around the keyword list
can be omitted as well. For example, the following:
String.split("1-0", "-", trim: true, parts: 2)
is equivalent to:
String.split("1-0", "-", [trim: true, parts: 2])
A keyword may have duplicated keys so it is not strictly
a key-value store. However most of the functions in this module
behave exactly as a dictionary so they work similarly to
the functions you would find in the `Map` module.
For example, `Keyword.get/3` will get the first entry matching
the given key, regardless if duplicated entries exist.
Similarly, `Keyword.put/3` and `Keyword.delete/3` ensure all
duplicated entries for a given key are removed when invoked.
Note that operations that require keys to be found in the keyword
list (like `Keyword.get/3`) need to traverse the list in order
to find keys, so these operations may be slower than their map
counterparts.
A handful of functions exist to handle duplicated keys, in
particular, `Enum.into/2` allows creating new keywords without
removing duplicated keys, `get_values/2` returns all values for
a given key and `delete_first/2` deletes just one of the existing
entries.
The functions in `Keyword` do not guarantee any property when
it comes to ordering. However, since a keyword list is simply a
list, all the operations defined in `Enum` and `List` can be
applied too, especially when ordering is required.
Most of the functions in this module work in linear time. This means
that, the time it takes to perform an operation grows at the same
rate as the length of the list.
"""
@compile :inline_list_funcs
@type key :: atom
@type value :: any
@type t :: [{key, value}]
@type t(value) :: [{key, value}]
@doc """
Returns `true` if `term` is a keyword list; otherwise returns `false`.
## Examples
iex> Keyword.keyword?([])
true
iex> Keyword.keyword?(a: 1)
true
iex> Keyword.keyword?([{Foo, 1}])
true
iex> Keyword.keyword?([{}])
false
iex> Keyword.keyword?([:key])
false
iex> Keyword.keyword?(%{})
false
"""
@spec keyword?(term) :: boolean
def keyword?(term)
def keyword?([{key, _value} | rest]) when is_atom(key), do: keyword?(rest)
def keyword?([]), do: true
def keyword?(_other), do: false
@doc """
Returns an empty keyword list, i.e. an empty list.
## Examples
iex> Keyword.new()
[]
"""
@spec new :: []
def new, do: []
@doc """
Creates a keyword list from an enumerable.
Duplicated entries are removed, the latest one prevails.
Unlike `Enum.into(enumerable, [])`, `Keyword.new(enumerable)`
guarantees the keys are unique.
## Examples
iex> Keyword.new([{:b, 1}, {:a, 2}])
[b: 1, a: 2]
iex> Keyword.new([{:a, 1}, {:a, 2}, {:a, 3}])
[a: 3]
"""
@spec new(Enum.t()) :: t
def new(pairs) do
new(pairs, fn pair -> pair end)
end
@doc """
Creates a keyword list from an enumerable via the transformation function.
Duplicated entries are removed, the latest one prevails.
Unlike `Enum.into(enumerable, [], fun)`,
`Keyword.new(enumerable, fun)` guarantees the keys are unique.
## Examples
iex> Keyword.new([:a, :b], fn x -> {x, x} end)
[a: :a, b: :b]
"""
@spec new(Enum.t(), (term -> {key, value})) :: t
def new(pairs, transform) when is_function(transform, 1) do
fun = fn el, acc ->
{k, v} = transform.(el)
put_new(acc, k, v)
end
:lists.foldl(fun, [], Enum.reverse(pairs))
end
@doc """
Gets the value for a specific `key`.
If `key` does not exist, return the default value
(`nil` if no default value).
If duplicated entries exist, the first one is returned.
Use `get_values/2` to retrieve all entries.
## Examples
iex> Keyword.get([], :a)
nil
iex> Keyword.get([a: 1], :a)
1
iex> Keyword.get([a: 1], :b)
nil
iex> Keyword.get([a: 1], :b, 3)
3
With duplicated keys:
iex> Keyword.get([a: 1, a: 2], :a, 3)
1
iex> Keyword.get([a: 1, a: 2], :b, 3)
3
"""
@spec get(t, key, value) :: value
def get(keywords, key, default \\ nil) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, value} -> value
false -> default
end
end
@doc """
Gets the value for a specific `key`.
If `key` does not exist, lazily evaluates `fun` and returns its result.
This is useful if the default value is very expensive to calculate or
generally difficult to setup and teardown again.
If duplicated entries exist, the first one is returned.
Use `get_values/2` to retrieve all entries.
## Examples
iex> keyword = [a: 1]
iex> fun = fn ->
...> # some expensive operation here
...> 13
...> end
iex> Keyword.get_lazy(keyword, :a, fun)
1
iex> Keyword.get_lazy(keyword, :b, fun)
13
"""
@spec get_lazy(t, key, (() -> value)) :: value
def get_lazy(keywords, key, fun)
when is_list(keywords) and is_atom(key) and is_function(fun, 0) do
case :lists.keyfind(key, 1, keywords) do
{^key, value} -> value
false -> fun.()
end
end
@doc """
Gets the value from `key` and updates it, all in one pass.
This `fun` argument receives the value of `key` (or `nil` if `key`
is not present) 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`. The `fun` may also
return `:pop`, implying the current value shall be removed from the
keyword list and returned.
The returned value is a tuple with the "get" value returned by
`fun` and a new keyword list with the updated value under `key`.
## Examples
iex> Keyword.get_and_update([a: 1], :a, fn current_value ->
...> {current_value, "new value!"}
...> end)
{1, [a: "new value!"]}
iex> Keyword.get_and_update([a: 1], :b, fn current_value ->
...> {current_value, "new value!"}
...> end)
{nil, [b: "new value!", a: 1]}
iex> Keyword.get_and_update([a: 1], :a, fn _ -> :pop end)
{1, []}
iex> Keyword.get_and_update([a: 1], :b, fn _ -> :pop end)
{nil, [a: 1]}
"""
@spec get_and_update(t, key, (value -> {get, value} | :pop)) :: {get, t} when get: term
def get_and_update(keywords, key, fun)
when is_list(keywords) and is_atom(key),
do: get_and_update(keywords, [], key, fun)
defp get_and_update([{key, current} | t], acc, key, fun) do
case fun.(current) do
{get, value} ->
{get, :lists.reverse(acc, [{key, value} | t])}
:pop ->
{current, :lists.reverse(acc, t)}
other ->
raise "the given function must return a two-element tuple or :pop, got: #{inspect(other)}"
end
end
defp get_and_update([{_, _} = h | t], acc, key, fun), do: get_and_update(t, [h | acc], key, fun)
defp get_and_update([], acc, key, fun) do
case fun.(nil) do
{get, update} ->
{get, [{key, update} | :lists.reverse(acc)]}
:pop ->
{nil, :lists.reverse(acc)}
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`.
This `fun` argument receives the value of `key` 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`.
The returned value is a tuple with the "get" value returned by `fun` and a new
keyword list with the updated value under `key`.
## Examples
iex> Keyword.get_and_update!([a: 1], :a, fn current_value ->
...> {current_value, "new value!"}
...> end)
{1, [a: "new value!"]}
iex> Keyword.get_and_update!([a: 1], :b, fn current_value ->
...> {current_value, "new value!"}
...> end)
** (KeyError) key :b not found in: [a: 1]
iex> Keyword.get_and_update!([a: 1], :a, fn _ ->
...> :pop
...> end)
{1, []}
"""
@spec get_and_update!(t, key, (value -> {get, value})) :: {get, t} when get: term
def get_and_update!(keywords, key, fun) do
get_and_update!(keywords, key, fun, [])
end
defp get_and_update!([{key, value} | keywords], key, fun, acc) do
case fun.(value) do
{get, value} ->
{get, :lists.reverse(acc, [{key, value} | delete(keywords, key)])}
:pop ->
{value, :lists.reverse(acc, keywords)}
other ->
raise "the given function must return a two-element tuple or :pop, got: #{inspect(other)}"
end
end
defp get_and_update!([{_, _} = e | keywords], key, fun, acc) do
get_and_update!(keywords, key, fun, [e | acc])
end
defp get_and_update!([], key, _fun, acc) when is_atom(key) do
raise(KeyError, key: key, term: acc)
end
@doc """
Fetches the value for a specific `key` and returns it in a tuple.
If the `key` does not exist, returns `:error`.
## Examples
iex> Keyword.fetch([a: 1], :a)
{:ok, 1}
iex> Keyword.fetch([a: 1], :b)
:error
"""
@spec fetch(t, key) :: {:ok, value} | :error
def fetch(keywords, key) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, value} -> {:ok, value}
false -> :error
end
end
@doc """
Fetches the value for specific `key`.
If `key` does not exist, a `KeyError` is raised.
## Examples
iex> Keyword.fetch!([a: 1], :a)
1
iex> Keyword.fetch!([a: 1], :b)
** (KeyError) key :b not found in: [a: 1]
"""
@spec fetch!(t, key) :: value
def fetch!(keywords, key) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, value} -> value
false -> raise(KeyError, key: key, term: keywords)
end
end
@doc """
Gets all values for a specific `key`.
## Examples
iex> Keyword.get_values([], :a)
[]
iex> Keyword.get_values([a: 1], :a)
[1]
iex> Keyword.get_values([a: 1, a: 2], :a)
[1, 2]
"""
@spec get_values(t, key) :: [value]
def get_values(keywords, key) when is_list(keywords) and is_atom(key) do
fun = fn
{^key, val} -> {true, val}
{_, _} -> false
end
:lists.filtermap(fun, keywords)
end
@doc """
Returns all keys from the keyword list.
Duplicated keys appear duplicated in the final list of keys.
## Examples
iex> Keyword.keys(a: 1, b: 2)
[:a, :b]
iex> Keyword.keys(a: 1, b: 2, a: 3)
[:a, :b, :a]
"""
@spec keys(t) :: [key]
def keys(keywords) when is_list(keywords) do
:lists.map(fn {k, _} -> k end, keywords)
end
@doc """
Returns all values from the keyword list.
Values from duplicated keys will be kept in the final list of values.
## Examples
iex> Keyword.values(a: 1, b: 2)
[1, 2]
iex> Keyword.values(a: 1, b: 2, a: 3)
[1, 2, 3]
"""
@spec values(t) :: [value]
def values(keywords) when is_list(keywords) do
:lists.map(fn {_, v} -> v end, keywords)
end
@doc """
Deletes the entries in the keyword list for a `key` with `value`.
If no `key` with `value` exists, returns the keyword list unchanged.
## Examples
iex> Keyword.delete([a: 1, b: 2], :a, 1)
[b: 2]
iex> Keyword.delete([a: 1, b: 2, a: 3], :a, 3)
[a: 1, b: 2]
iex> Keyword.delete([a: 1], :a, 5)
[a: 1]
iex> Keyword.delete([a: 1], :b, 5)
[a: 1]
"""
@spec delete(t, key, value) :: t
def delete(keywords, key, value) when is_list(keywords) and is_atom(key) do
case :lists.keymember(key, 1, keywords) do
true -> delete_key_value(keywords, key, value)
_ -> keywords
end
end
defp delete_key_value([{key, value} | tail], key, value) do
delete_key_value(tail, key, value)
end
defp delete_key_value([{_, _} = pair | tail], key, value) do
[pair | delete_key_value(tail, key, value)]
end
defp delete_key_value([], _key, _value) do
[]
end
@doc """
Deletes the entries in the keyword list for a specific `key`.
If the `key` does not exist, returns the keyword list unchanged.
Use `delete_first/2` to delete just the first entry in case of
duplicated keys.
## Examples
iex> Keyword.delete([a: 1, b: 2], :a)
[b: 2]
iex> Keyword.delete([a: 1, b: 2, a: 3], :a)
[b: 2]
iex> Keyword.delete([b: 2], :a)
[b: 2]
"""
@spec delete(t, key) :: t
@compile {:inline, delete: 2}
def delete(keywords, key) when is_list(keywords) and is_atom(key) do
case :lists.keymember(key, 1, keywords) do
true -> delete_key(keywords, key)
_ -> keywords
end
end
defp delete_key([{key, _} | tail], key) do
delete_key(tail, key)
end
defp delete_key([{_, _} = pair | tail], key) do
[pair | delete_key(tail, key)]
end
defp delete_key([], _key) do
[]
end
@doc """
Deletes the first entry in the keyword list for a specific `key`.
If the `key` does not exist, returns the keyword list unchanged.
## Examples
iex> Keyword.delete_first([a: 1, b: 2, a: 3], :a)
[b: 2, a: 3]
iex> Keyword.delete_first([b: 2], :a)
[b: 2]
"""
@spec delete_first(t, key) :: t
def delete_first(keywords, key) when is_list(keywords) and is_atom(key) do
case :lists.keymember(key, 1, keywords) do
true -> delete_first_key(keywords, key)
_ -> keywords
end
end
defp delete_first_key([{key, _} | tail], key) do
tail
end
defp delete_first_key([{_, _} = pair | tail], key) do
[pair | delete_first_key(tail, key)]
end
defp delete_first_key([], _key) do
[]
end
@doc """
Puts the given `value` under `key`.
If a previous value is already stored, all entries are
removed and the value is overridden.
## Examples
iex> Keyword.put([a: 1], :b, 2)
[b: 2, a: 1]
iex> Keyword.put([a: 1, b: 2], :a, 3)
[a: 3, b: 2]
iex> Keyword.put([a: 1, b: 2, a: 4], :a, 3)
[a: 3, b: 2]
"""
@spec put(t, key, value) :: t
def put(keywords, key, value) when is_list(keywords) and is_atom(key) do
[{key, value} | delete(keywords, key)]
end
@doc """
Evaluates `fun` and puts the result under `key`
in keyword list unless `key` is already present.
This is useful if the value is very expensive to calculate or
generally difficult to setup and teardown again.
## Examples
iex> keyword = [a: 1]
iex> fun = fn ->
...> # some expensive operation here
...> 3
...> end
iex> Keyword.put_new_lazy(keyword, :a, fun)
[a: 1]
iex> Keyword.put_new_lazy(keyword, :b, fun)
[b: 3, a: 1]
"""
@spec put_new_lazy(t, key, (() -> value)) :: t
def put_new_lazy(keywords, key, fun)
when is_list(keywords) and is_atom(key) and is_function(fun, 0) do
case :lists.keyfind(key, 1, keywords) do
{^key, _} -> keywords
false -> [{key, fun.()} | keywords]
end
end
@doc """
Puts the given `value` under `key` unless the entry `key`
already exists.
## Examples
iex> Keyword.put_new([a: 1], :b, 2)
[b: 2, a: 1]
iex> Keyword.put_new([a: 1, b: 2], :a, 3)
[a: 1, b: 2]
"""
@spec put_new(t, key, value) :: t
def put_new(keywords, key, value) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, _} -> keywords
false -> [{key, value} | keywords]
end
end
@doc false
@deprecated "Use Keyword.fetch/2 + Keyword.put/3 instead"
def replace(keywords, key, value) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, _} -> [{key, value} | delete(keywords, key)]
false -> keywords
end
end
@doc """
Alters the value stored under `key` to `value`, but only
if the entry `key` already exists in `keywords`.
If `key` is not present in `keywords`, a `KeyError` exception is raised.
## Examples
iex> Keyword.replace!([a: 1, b: 2, a: 4], :a, 3)
[a: 3, b: 2]
iex> Keyword.replace!([a: 1], :b, 2)
** (KeyError) key :b not found in: [a: 1]
"""
@doc since: "1.5.0"
@spec replace!(t, key, value) :: t
def replace!(keywords, key, value) when is_list(keywords) and is_atom(key) do
case :lists.keyfind(key, 1, keywords) do
{^key, _} -> [{key, value} | delete(keywords, key)]
false -> raise KeyError, key: key, term: keywords
end
end
@doc """
Checks if two keywords are equal.
Two keywords are considered to be equal if they contain
the same keys and those keys contain the same values.
## Examples
iex> Keyword.equal?([a: 1, b: 2], [b: 2, a: 1])
true
iex> Keyword.equal?([a: 1, b: 2], [b: 1, a: 2])
false
iex> Keyword.equal?([a: 1, b: 2, a: 3], [b: 2, a: 3, a: 1])
true
"""
@spec equal?(t, t) :: boolean
def equal?(left, right) when is_list(left) and is_list(right) do
:lists.sort(left) == :lists.sort(right)
end
@doc """
Merges two keyword lists into one.
All keys, including duplicated keys, given in `keywords2` will be added
to `keywords1`, overriding any existing one.
There are no guarantees about the order of keys in the returned keyword.
## Examples
iex> Keyword.merge([a: 1, b: 2], [a: 3, d: 4])
[b: 2, a: 3, d: 4]
iex> Keyword.merge([a: 1, b: 2], [a: 3, d: 4, a: 5])
[b: 2, a: 3, d: 4, a: 5]
iex> Keyword.merge([a: 1], [2, 3])
** (ArgumentError) expected a keyword list as the second argument, got: [2, 3]
"""
@spec merge(t, t) :: t
def merge(keywords1, keywords2)
def merge(keywords1, []) when is_list(keywords1), do: keywords1
def merge([], keywords2) when is_list(keywords2), do: keywords2
def merge(keywords1, keywords2) when is_list(keywords1) and is_list(keywords2) do
if keyword?(keywords2) do
fun = fn
{key, _value} when is_atom(key) ->
not has_key?(keywords2, key)
_ ->
raise ArgumentError,
"expected a keyword list as the first argument, got: #{inspect(keywords1)}"
end
:lists.filter(fun, keywords1) ++ keywords2
else
raise ArgumentError,
"expected a keyword list as the second argument, got: #{inspect(keywords2)}"
end
end
@doc """
Merges two keyword lists into one.
All keys, including duplicated keys, given in `keywords2` will be added
to `keywords1`. The given function will be invoked to solve conflicts.
If `keywords2` has duplicate keys, the given function will be invoked
for each matching pair in `keywords1`.
There are no guarantees about the order of keys in the returned keyword.
## Examples
iex> Keyword.merge([a: 1, b: 2], [a: 3, d: 4], fn _k, v1, v2 ->
...> v1 + v2
...> end)
[b: 2, a: 4, d: 4]
iex> Keyword.merge([a: 1, b: 2], [a: 3, d: 4, a: 5], fn :a, v1, v2 ->
...> v1 + v2
...> end)
[b: 2, a: 4, d: 4, a: 5]
iex> Keyword.merge([a: 1, b: 2, a: 3], [a: 3, d: 4, a: 5], fn :a, v1, v2 ->
...> v1 + v2
...> end)
[b: 2, a: 4, d: 4, a: 8]
iex> Keyword.merge([a: 1, b: 2], [:a, :b], fn :a, v1, v2 ->
...> v1 + v2
...> end)
** (ArgumentError) expected a keyword list as the second argument, got: [:a, :b]
"""
@spec merge(t, t, (key, value, value -> value)) :: t
def merge(keywords1, keywords2, fun)
when is_list(keywords1) and is_list(keywords2) and is_function(fun, 3) do
if keyword?(keywords1) do
do_merge(keywords2, [], keywords1, keywords1, fun, keywords2)
else
raise ArgumentError,
"expected a keyword list as the first argument, got: #{inspect(keywords1)}"
end
end
defp do_merge([{key, value2} | tail], acc, rest, original, fun, keywords2) when is_atom(key) do
case :lists.keyfind(key, 1, original) do
{^key, value1} ->
acc = [{key, fun.(key, value1, value2)} | acc]
original = :lists.keydelete(key, 1, original)
do_merge(tail, acc, delete(rest, key), original, fun, keywords2)
false ->
do_merge(tail, [{key, value2} | acc], rest, original, fun, keywords2)
end
end
defp do_merge([], acc, rest, _original, _fun, _keywords2) do
rest ++ :lists.reverse(acc)
end
defp do_merge(_other, _acc, _rest, _original, _fun, keywords2) do
raise ArgumentError,
"expected a keyword list as the second argument, got: #{inspect(keywords2)}"
end
@doc """
Returns whether a given `key` exists in the given `keywords`.
## Examples
iex> Keyword.has_key?([a: 1], :a)
true
iex> Keyword.has_key?([a: 1], :b)
false
"""
@spec has_key?(t, key) :: boolean
def has_key?(keywords, key) when is_list(keywords) and is_atom(key) do
:lists.keymember(key, 1, keywords)
end
@doc """
Updates the `key` with the given function.
If the `key` does not exist, raises `KeyError`.
If there are duplicated keys, they are all removed and only the first one
is updated.
## Examples
iex> Keyword.update!([a: 1], :a, &(&1 * 2))
[a: 2]
iex> Keyword.update!([a: 1, a: 2], :a, &(&1 * 2))
[a: 2]
iex> Keyword.update!([a: 1], :b, &(&1 * 2))
** (KeyError) key :b not found in: [a: 1]
"""
@spec update!(t, key, (value -> value)) :: t
def update!(keywords, key, fun)
when is_list(keywords) and is_atom(key) and is_function(fun, 1) do
update!(keywords, key, fun, keywords)
end
defp update!([{key, value} | keywords], key, fun, _dict) do
[{key, fun.(value)} | delete(keywords, key)]
end
defp update!([{_, _} = e | keywords], key, fun, dict) do
[e | update!(keywords, key, fun, dict)]
end
defp update!([], key, _fun, dict) when is_atom(key) do
raise(KeyError, key: key, term: dict)
end
@doc """
Updates the `key` in `keywords` with the given function.
If the `key` does not exist, inserts the given `initial` value.
If there are duplicated keys, they are all removed and only the first one
is updated.
## Examples
iex> Keyword.update([a: 1], :a, 13, &(&1 * 2))
[a: 2]
iex> Keyword.update([a: 1, a: 2], :a, 13, &(&1 * 2))
[a: 2]
iex> Keyword.update([a: 1], :b, 11, &(&1 * 2))
[a: 1, b: 11]
"""
@spec update(t, key, value, (value -> value)) :: t
def update(keywords, key, initial, fun)
def update([{key, value} | keywords], key, _initial, fun) do
[{key, fun.(value)} | delete(keywords, key)]
end
def update([{_, _} = e | keywords], key, initial, fun) do
[e | update(keywords, key, initial, fun)]
end
def update([], key, initial, _fun) when is_atom(key) do
[{key, initial}]
end
@doc """
Takes all entries corresponding to the given keys and extracts them into a
separate keyword list.
Returns a tuple with the new list and the old list with removed keys.
Keys for which there are no entries in the keyword list are ignored.
Entries with duplicated keys end up in the same keyword list.
## Examples
iex> Keyword.split([a: 1, b: 2, c: 3], [:a, :c, :e])
{[a: 1, c: 3], [b: 2]}
iex> Keyword.split([a: 1, b: 2, c: 3, a: 4], [:a, :c, :e])
{[a: 1, c: 3, a: 4], [b: 2]}
"""
@spec split(t, [key]) :: {t, t}
def split(keywords, keys) when is_list(keywords) and is_list(keys) do
fun = fn {k, v}, {take, drop} ->
case k in keys do
true -> {[{k, v} | take], drop}
false -> {take, [{k, v} | drop]}
end
end
acc = {[], []}
{take, drop} = :lists.foldl(fun, acc, keywords)
{:lists.reverse(take), :lists.reverse(drop)}
end
@doc """
Takes all entries corresponding to the given keys and returns them in a new
keyword list.
Duplicated keys are preserved in the new keyword list.
## Examples
iex> Keyword.take([a: 1, b: 2, c: 3], [:a, :c, :e])
[a: 1, c: 3]
iex> Keyword.take([a: 1, b: 2, c: 3, a: 5], [:a, :c, :e])
[a: 1, c: 3, a: 5]
"""
@spec take(t, [key]) :: t
def take(keywords, keys) when is_list(keywords) and is_list(keys) do
:lists.filter(fn {k, _} -> k in keys end, keywords)
end
@doc """
Drops the given keys from the keyword list.
Duplicated keys are preserved in the new keyword list.
## Examples
iex> Keyword.drop([a: 1, b: 2, c: 3], [:b, :d])
[a: 1, c: 3]
iex> Keyword.drop([a: 1, b: 2, b: 3, c: 3, a: 5], [:b, :d])
[a: 1, c: 3, a: 5]
"""
@spec drop(t, [key]) :: t
def drop(keywords, keys) when is_list(keywords) and is_list(keys) do
:lists.filter(fn {key, _} -> key not in keys end, keywords)
end
@doc """
Returns the first value for `key` and removes all associated entries in the keyword list.
It returns a tuple where the first element is the first value for `key` and the
second element is a keyword list with all entries associated with `key` removed.
If the `key` is not present in the keyword list, `{default, keyword_list}` is
returned.
If you don't want to remove all the entries associated with `key` use `pop_first/3`
instead, that function will remove only the first entry.
## Examples
iex> Keyword.pop([a: 1], :a)
{1, []}
iex> Keyword.pop([a: 1], :b)
{nil, [a: 1]}
iex> Keyword.pop([a: 1], :b, 3)
{3, [a: 1]}
iex> Keyword.pop([a: 1, a: 2], :a)
{1, []}
"""
@spec pop(t, key, value) :: {value, t}
def pop(keywords, key, default \\ nil) when is_list(keywords) and is_atom(key) do
case fetch(keywords, key) do
{:ok, value} ->
{value, delete(keywords, key)}
:error ->
{default, keywords}
end
end
@doc """
Lazily returns and removes all values associated with `key` in the keyword list.
This is useful if the default value is very expensive to calculate or
generally difficult to setup and teardown again.
All duplicated keys are removed. See `pop_first/3` for
removing only the first entry.
## Examples
iex> keyword = [a: 1]
iex> fun = fn ->
...> # some expensive operation here