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
|
;;; list.el --- Functions for working with lists. -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;;; Commentary:
;; Since I prefer having the `list/' namespace, I wrote this module to wrap many
;; of the functions that are defined in the the global namespace in ELisp. I
;; sometimes forget the names of these functions, so it's nice for them to be
;; organized like this.
;;
;; Motivation:
;; Here are some examples of function names that I cannot tolerate:
;; - `car': Return the first element (i.e. "head") of a linked list
;; - `cdr': Return the tail of a linked list
;; As are most APIs for standard libraries that I write, this is heavily
;; influenced by Elixir's standard library.
;;
;; Elixir's List library:
;; - ++/2
;; - --/2
;; - hd/1
;; - tl/1
;; - in/2
;; - length/1
;;
;; Similar libraries:
;; - dash.el: Functional library that mimmicks Clojure. It is consumed herein.
;; - list-utils.el: Utility library that covers things that dash.el may not
;; cover.
;; stream.el: Elisp implementation of streams, "implemented as delayed
;; evaluation of cons cells."
;; TODO: Consider naming this file linked-list.el.
;; TODO: Support module-like macro that auto-namespaces functions.
;; TODO: Consider wrapping most data structures like linked-lists,
;; associative-lists, etc in a `cl-defstruct', so that the dispatching by type
;; can be nominal instead of duck-typing. I'm not sure if this is a good idea
;; or not. If I do this, I should provide isomorphisms to map between idiomatic
;; ways of working with Elisp data structures and my wrapped variants.
;; TODO: Are function aliases/synonyms even a good idea? Or do they just
;; bloat the API unnecessarily?
;;; Code:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Dependencies
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(require 'prelude)
(require 'dash)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Constants
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defconst list/tests? t
"When t, run the test suite.")
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Library
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun list/new ()
"Return a new, empty list."
'())
(defun list/concat (&rest lists)
"Joins `LISTS' into on list."
(apply #'-concat lists))
(defun list/join (joint xs)
"Join a list of strings, XS, with JOINT."
(if (list/empty? xs)
""
(list/reduce (list/first xs)
(lambda (x acc)
(string/concat acc joint x))
(list/tail xs))))
(defun list/length (xs)
"Return the number of elements in `XS'."
(length xs))
(defun list/get (i xs)
"Return the value in `XS' at `I', or nil."
(nth i xs))
(defun list/head (xs)
"Return the head of `XS'."
(car xs))
;; TODO: Learn how to write proper function aliases.
(defun list/first (xs)
"Alias for `list/head' for `XS'."
(list/head xs))
(defun list/tail (xs)
"Return the tail of `XS'."
(cdr xs))
(defun list/reverse (xs)
"Reverses `XS'."
(reverse xs))
(defun list/cons (x xs)
"Add `X' to the head of `XS'."
(cons x xs))
;; map, filter, reduce
;; TODO: Create function adapters like swap.
;; (defun adapter/swap (f)
;; "Return a new function that wraps `F' and swaps the arguments."
;; (lambda (a b)
;; (funcall f b a)))
;; TODO: Make this function work.
(defun list/reduce (acc f xs)
"Return over `XS' calling `F' on an element in `XS'and `ACC'."
(-reduce-from (lambda (acc x) (funcall f x acc)) acc xs))
(defun list/map (f xs)
"Call `F' on each element of `XS'."
(-map f xs))
(defun list/map-indexed (f xs)
"Call `F' on each element of `XS' along with its index."
(-map-indexed (lambda (i x) (funcall f x i)) xs))
(defun list/filter (p xs)
"Return a subset of XS where predicate P returned t."
(list/reverse
(list/reduce
'()
(lambda (x acc)
(if (funcall p x)
(list/cons x acc)
acc))
xs)))
(defun list/reject (p xs)
"Return a subset of XS where predicate of P return nil."
(list/filter (lambda (x) (not (funcall p x))) xs))
(defun list/find (p xs)
"Return the first x in XS that passes P or nil."
(-find p xs))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Predicates
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun list/instance? (xs)
"Return t if `XS' is a list.
Be leery of using this with things like alists. Many data structures in Elisp
are implemented using linked lists."
(listp xs))
(defun list/empty? (xs)
"Return t if XS are empty."
(= 0 (list/length xs)))
(defun list/all? (p xs)
"Return t if all `XS' pass the predicate, `P'."
(-all? p xs))
(defun list/any? (p xs)
"Return t if any `XS' pass the predicate, `P'."
(-any? p xs))
(defun list/contains? (x xs)
"Return t if X is in XS using `equal'."
(-contains? xs x))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Tests
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(when list/tests?
(prelude/assert
(= 0
(list/length '())))
(prelude/assert
(= 5
(list/length '(1 2 3 4 5))))
(prelude/assert
(= 16
(list/reduce 1 (lambda (x acc) (+ x acc)) '(1 2 3 4 5))))
(prelude/assert
(equal '(2 4 6 8 10)
(list/map (lambda (x) (* x 2)) '(1 2 3 4 5)))))
(provide 'list)
;;; list.el ends here
|
