Add -common-prefix

Re: #260
8 years ago · 72b8d39458
parent 528e5a51f1
commit 72b8d39458
6 changed files with 200 additions and 136 deletions
--- a/README.md
+++ b/README.md
@ -146,6 +146,7 @@ Functions reducing lists into single value.
 * [-running-product](#-running-product-list) `(list)`
 * [-inits](#-inits-list) `(list)`
 * [-tails](#-tails-list) `(list)`
+* [-common-prefix](#-common-prefix-rest-lists) `(&rest lists)`
 * [-min](#-min-list) `(list)`
 * [-min-by](#-min-by-comparator-list) `(comparator list)`
 * [-max](#-max-list) `(list)`
@ -1043,6 +1044,16 @@ Return all suffixes of `list`
 (-tails '(1)) ;; => '((1) nil)
 ```

+#### -common-prefix `(&rest lists)`
+
+Return the longest common prefix of `lists`.
+
+```el
+(-common-prefix '(1)) ;; => '(1)
+(-common-prefix '(1 2) nil '(1 2)) ;; => nil
+(-common-prefix '(1 2) '(1 2 3) '(1 2 3 4)) ;; => '(1 2)
+```
+
 #### -min `(list)`

 Return the smallest value from `list` of numbers or markers.
@ -2907,6 +2918,7 @@ Change `readme-template.md` or `examples-to-docs.el` instead.
 - [Vasilij Schneidermann](https://github.com/wasamasa) contributed `-some`.
 - [William West](https://github.com/occidens) made `-fixfn` more robust at handling floats.
 - [Cam Saül](https://github.com/camsaul) contributed `-some->`, `-some->>`, and `-some-->`.
+ - [Basil L. Contovounesios](https://github.com/basil-conto) contributed `-common-prefix`.

 Thanks!

--- a/dash.el
+++ b/dash.el
@ -2115,6 +2115,15 @@ or with `-compare-fn' if that's non-nil."
  "Return all suffixes of LIST"
  (-reductions-r-from 'cons nil list))

+(defun -common-prefix (&rest lists)
+  "Return the longest common prefix of LISTS."
+  (declare (pure t) (side-effect-free t))
+  (--reduce (let (head prefix)
+              (while (and acc it (equal (setq head (pop acc)) (pop it)))
+                (push head prefix))
+              (nreverse prefix))
+            lists))
+
 (defun -contains? (list element)
  "Return non-nil if LIST contains ELEMENT.

@ -2687,6 +2696,7 @@ structure such as plist or alist."
                             "-permutations"
                             "-inits"
                             "-tails"
+                             "-common-prefix"
                             "-contains?"
                             "-contains-p"
                             "-same-items?"
--- a/dash.info
+++ b/dash.info
@ -938,6 +938,16 @@ Functions reducing lists into single value.
          (-tails '(1))
              ⇒ '((1) nil)

+ -- Function: -common-prefix (&rest lists)
+     Return the longest common prefix of LISTS.
+
+          (-common-prefix '(1))
+              ⇒ '(1)
+          (-common-prefix '(1 2) nil '(1 2))
+              ⇒ nil
+          (-common-prefix '(1 2) '(1 2 3) '(1 2 3 4))
+              ⇒ '(1 2)
+
 -- Function: -min (list)
     Return the smallest value from LIST of numbers or markers.

@ -2871,6 +2881,7 @@ Index
 * -butlast:                              Other list operations.
                                                            (line 311)
 * -clone:                                Tree operations.   (line 123)
+* -common-prefix:                        Reductions.        (line 225)
 * -compose:                              Function combinators.
                                                            (line  42)
 * -concat:                               List to list.      (line  22)
@ -2953,10 +2964,10 @@ Index
 * -map-last:                             Maps.              (line  52)
 * -map-when:                             Maps.              (line  21)
 * -mapcat:                               Maps.              (line 124)
-* -max:                                  Reductions.        (line 249)
-* -max-by:                               Reductions.        (line 259)
-* -min:                                  Reductions.        (line 225)
-* -min-by:                               Reductions.        (line 235)
+* -max:                                  Reductions.        (line 259)
+* -max-by:                               Reductions.        (line 269)
+* -min:                                  Reductions.        (line 235)
+* -min-by:                               Reductions.        (line 245)
 * -non-nil:                              Sublist selection. (line  80)
 * -none?:                                Predicates.        (line  30)
 * -not:                                  Function combinators.
@ -3131,138 +3142,139 @@ Ref: -product29402
 Ref: -running-product29611
 Ref: -inits29924
 Ref: -tails30172
-Ref: -min30419
-Ref: -min-by30645
-Ref: -max31168
-Ref: -max-by31393
-Node: Unfolding31921
-Ref: -iterate32160
-Ref: -unfold32605
-Node: Predicates33413
-Ref: -any?33537
-Ref: -all?33857
-Ref: -none?34187
-Ref: -only-some?34489
-Ref: -contains?34974
-Ref: -same-items?35363
-Ref: -is-prefix?35748
-Ref: -is-suffix?36071
-Ref: -is-infix?36394
-Node: Partitioning36748
-Ref: -split-at36936
-Ref: -split-with37221
-Ref: -split-on37624
-Ref: -split-when38300
-Ref: -separate38940
-Ref: -partition39382
-Ref: -partition-all39834
-Ref: -partition-in-steps40262
-Ref: -partition-all-in-steps40759
-Ref: -partition-by41244
-Ref: -partition-by-header41626
-Ref: -partition-after-pred42230
-Ref: -partition-before-pred42601
-Ref: -partition-before-item42979
-Ref: -partition-after-item43290
-Ref: -group-by43596
-Node: Indexing44033
-Ref: -elem-index44235
-Ref: -elem-indices44630
-Ref: -find-index45013
-Ref: -find-last-index45502
-Ref: -find-indices46006
-Ref: -grade-up46414
-Ref: -grade-down46817
-Node: Set operations47227
-Ref: -union47410
-Ref: -difference47852
-Ref: -intersection48269
-Ref: -powerset48706
-Ref: -permutations48919
-Ref: -distinct49219
-Node: Other list operations49543
-Ref: -rotate49768
-Ref: -repeat50063
-Ref: -cons*50326
-Ref: -snoc50713
-Ref: -interpose51126
-Ref: -interleave51424
-Ref: -zip-with51793
-Ref: -zip52510
-Ref: -zip-fill53316
-Ref: -unzip53639
-Ref: -cycle54173
-Ref: -pad54546
-Ref: -table54869
-Ref: -table-flat55659
-Ref: -first56668
-Ref: -some57040
-Ref: -last57349
-Ref: -first-item57683
-Ref: -second-item58099
-Ref: -third-item58379
-Ref: -fourth-item58657
-Ref: -fifth-item58923
-Ref: -last-item59185
-Ref: -butlast59477
-Ref: -sort59724
-Ref: -list60212
-Ref: -fix60543
-Node: Tree operations61083
-Ref: -tree-seq61279
-Ref: -tree-map62137
-Ref: -tree-map-nodes62580
-Ref: -tree-reduce63435
-Ref: -tree-reduce-from64317
-Ref: -tree-mapreduce64918
-Ref: -tree-mapreduce-from65778
-Ref: -clone67064
-Node: Threading macros67392
-Ref: ->67537
-Ref: ->>68029
-Ref: -->68534
-Ref: -as->69095
-Ref: -some->69550
-Ref: -some->>69924
-Ref: -some-->70360
-Node: Binding70831
-Ref: -when-let71043
-Ref: -when-let*71528
-Ref: -if-let72056
-Ref: -if-let*72451
-Ref: -let73068
-Ref: -let*77861
-Ref: -lambda78802
-Node: Side-effects79604
-Ref: -each79798
-Ref: -each-while80205
-Ref: -each-indexed80565
-Ref: -dotimes81083
-Ref: -doto81386
-Node: Destructive operations81813
-Ref: !cons81986
-Ref: !cdr82192
-Node: Function combinators82387
-Ref: -partial82661
-Ref: -rpartial83056
-Ref: -juxt83458
-Ref: -compose83890
-Ref: -applify84448
-Ref: -on84895
-Ref: -flip85418
-Ref: -const85730
-Ref: -cut86074
-Ref: -not86560
-Ref: -orfn86870
-Ref: -andfn87304
-Ref: -iteratefn87799
-Ref: -fixfn88502
-Ref: -prodfn90071
-Node: Development91137
-Node: Contribute91486
-Node: Changes92234
-Node: Contributors95233
-Node: Index96857
+Ref: -common-prefix30419
+Ref: -min30713
+Ref: -min-by30939
+Ref: -max31462
+Ref: -max-by31687
+Node: Unfolding32215
+Ref: -iterate32454
+Ref: -unfold32899
+Node: Predicates33707
+Ref: -any?33831
+Ref: -all?34151
+Ref: -none?34481
+Ref: -only-some?34783
+Ref: -contains?35268
+Ref: -same-items?35657
+Ref: -is-prefix?36042
+Ref: -is-suffix?36365
+Ref: -is-infix?36688
+Node: Partitioning37042
+Ref: -split-at37230
+Ref: -split-with37515
+Ref: -split-on37918
+Ref: -split-when38594
+Ref: -separate39234
+Ref: -partition39676
+Ref: -partition-all40128
+Ref: -partition-in-steps40556
+Ref: -partition-all-in-steps41053
+Ref: -partition-by41538
+Ref: -partition-by-header41920
+Ref: -partition-after-pred42524
+Ref: -partition-before-pred42895
+Ref: -partition-before-item43273
+Ref: -partition-after-item43584
+Ref: -group-by43890
+Node: Indexing44327
+Ref: -elem-index44529
+Ref: -elem-indices44924
+Ref: -find-index45307
+Ref: -find-last-index45796
+Ref: -find-indices46300
+Ref: -grade-up46708
+Ref: -grade-down47111
+Node: Set operations47521
+Ref: -union47704
+Ref: -difference48146
+Ref: -intersection48563
+Ref: -powerset49000
+Ref: -permutations49213
+Ref: -distinct49513
+Node: Other list operations49837
+Ref: -rotate50062
+Ref: -repeat50357
+Ref: -cons*50620
+Ref: -snoc51007
+Ref: -interpose51420
+Ref: -interleave51718
+Ref: -zip-with52087
+Ref: -zip52804
+Ref: -zip-fill53610
+Ref: -unzip53933
+Ref: -cycle54467
+Ref: -pad54840
+Ref: -table55163
+Ref: -table-flat55953
+Ref: -first56962
+Ref: -some57334
+Ref: -last57643
+Ref: -first-item57977
+Ref: -second-item58393
+Ref: -third-item58673
+Ref: -fourth-item58951
+Ref: -fifth-item59217
+Ref: -last-item59479
+Ref: -butlast59771
+Ref: -sort60018
+Ref: -list60506
+Ref: -fix60837
+Node: Tree operations61377
+Ref: -tree-seq61573
+Ref: -tree-map62431
+Ref: -tree-map-nodes62874
+Ref: -tree-reduce63729
+Ref: -tree-reduce-from64611
+Ref: -tree-mapreduce65212
+Ref: -tree-mapreduce-from66072
+Ref: -clone67358
+Node: Threading macros67686
+Ref: ->67831
+Ref: ->>68323
+Ref: -->68828
+Ref: -as->69389
+Ref: -some->69844
+Ref: -some->>70218
+Ref: -some-->70654
+Node: Binding71125
+Ref: -when-let71337
+Ref: -when-let*71822
+Ref: -if-let72350
+Ref: -if-let*72745
+Ref: -let73362
+Ref: -let*78155
+Ref: -lambda79096
+Node: Side-effects79898
+Ref: -each80092
+Ref: -each-while80499
+Ref: -each-indexed80859
+Ref: -dotimes81377
+Ref: -doto81680
+Node: Destructive operations82107
+Ref: !cons82280
+Ref: !cdr82486
+Node: Function combinators82681
+Ref: -partial82955
+Ref: -rpartial83350
+Ref: -juxt83752
+Ref: -compose84184
+Ref: -applify84742
+Ref: -on85189
+Ref: -flip85712
+Ref: -const86024
+Ref: -cut86368
+Ref: -not86854
+Ref: -orfn87164
+Ref: -andfn87598
+Ref: -iteratefn88093
+Ref: -fixfn88796
+Ref: -prodfn90365
+Node: Development91431
+Node: Contribute91780
+Node: Changes92528
+Node: Contributors95527
+Node: Index97151

 End Tag Table

--- a/dash.texi
+++ b/dash.texi
@ -1416,6 +1416,26 @@ Return all suffixes of @var{list}
@end example
@end defun

+@anchor{-common-prefix}
+@defun -common-prefix (&rest lists)
+Return the longest common prefix of @var{lists}.
+
+@example
+@group
+(-common-prefix '(1))
+    @result{} '(1)
+@end group
+@group
+(-common-prefix '(1 2) nil '(1 2))
+    @result{} nil
+@end group
+@group
+(-common-prefix '(1 2) '(1 2 3) '(1 2 3 4))
+    @result{} '(1 2)
+@end group
+@end example
+@end defun
+
@anchor{-min}
@defun -min (list)
 Return the smallest value from @var{list} of numbers or markers.
--- a/dev/examples.el
+++ b/dev/examples.el
@ -387,6 +387,15 @@ new list."
    (-tails nil) => '(nil)
    (-tails '(1)) => '((1) nil))

+  (defexamples -common-prefix
+    (-common-prefix '(1)) => '(1)
+    (-common-prefix '(1 2) () '(1 2)) => ()
+    (-common-prefix '(1 2) '(1 2 3) '(1 2 3 4)) => '(1 2)
+    (-common-prefix '(())) => '(())
+    (-common-prefix () ()) => ()
+    (-common-prefix ()) => ()
+    (-common-prefix) => ())
+
  (defexamples -min
    (-min '(0)) => 0
    (-min '(3 2 1)) => 1
--- a/readme-template.md
+++ b/readme-template.md
@ -245,6 +245,7 @@ Change `readme-template.md` or `examples-to-docs.el` instead.
 - [Vasilij Schneidermann](https://github.com/wasamasa) contributed `-some`.
 - [William West](https://github.com/occidens) made `-fixfn` more robust at handling floats.
 - [Cam Saül](https://github.com/camsaul) contributed `-some->`, `-some->>`, and `-some-->`.
+ - [Basil L. Contovounesios](https://github.com/basil-conto) contributed `-common-prefix`.

 Thanks!