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
|
Generators
==========
.. module:: fun
This section contains a number of useful generators modeled after Standard ML,
Haskell, Python, Ruby, JavaScript and other languages.
Finite Generators
-----------------
.. function:: range([start,] stop[, step])
:param start: an endpoint of the interval (see below)
:type start: number
:param stop: an endpoint of the interval (see below)
:type stop: number
:param step: a step
:type step: number
:returns: an iterator
The iterator to create arithmetic progressions. Iteration values are generated
within closed interval ``[start, stop]`` (i.e. *stop* is included).
If the *start* argument is omitted, it defaults to ``1`` (*stop* > 0) or
to ``-1`` (*stop* < 0). If the *step* argument is omitted, it defaults to
``1`` (*start* <= *stop*) or to ``-1`` (*start* > *stop*). If *step* is
positive, the last element is the largest ``start + i * step`` less than or
equal to *stop*; if *step* is negative, the last element is the smallest
``start + i * step`` greater than or equal to *stop*.
*step* must not be zero (or else an error is raised).
``range(0)`` returns empty iterator.
Examples:
.. code-block:: lua
> for _it, v in range(5) do print(v) end
1
2
3
4
5
> for _it, v in range(-5) do print(v) end
-1
-2
-3
-4
-5
> for _it, v in range(1, 6) do print(v) end
1
2
3
4
5
6
> for _it, v in range(0, 20, 5) do print(v) end
0
5
10
15
20
> for _it, v in range(0, 10, 3) do print(v) end
0
3
6
9
> for _it, v in range(0, 1.5, 0.2) do print(v) end
0
0.2
0.4
0.6
0.8
1
1.2
1.4
> for _it, v in range(0) do print(v) end
> for _it, v in range(1) do print(v) end
1
> for _it, v in range(1, 0) do print(v) end
1
0
> for _it, v in range(0, 10, 0) do print(v) end
error: step must not be zero
Infinity Generators
-------------------
.. function:: duplicate(...)
:param ...: objects to duplicate
:type ...: non nil
:returns: an iterator
The iterator returns values over and over again indefinitely. All values
that passed to the iterator are returned as-is during the iteration.
Examples:
.. code-block:: lua
> each(print, take(3, duplicate('a', 'b', 'c')))
a b c
a b c
> each(print, take(3, duplicate('x')))
x
x
x
> for _it, a, b, c, d, e in take(3, duplicate(1, 2, 'a', 3, 'b')) do
print(a, b, c, d, e)
>> end
1 2 a 3 b
1 2 a 3 b
1 2 a 3 b
.. function:: xrepeat(...)
An alias for :func:`duplicate`.
.. function:: replicate(...)
An alias for :func:`duplicate`.
.. function:: tabulate(fun)
:param fun: an unary generating function
:type fun: function(n: uint) -> ...
:returns: an iterator
The iterator that returns ``fun(0)``, ``fun(1)``, ``fun(2)``, ``...`` values
indefinitely.
Examples:
.. code-block:: lua
> each(print, take(5, tabulate(function(x) return 'a', 'b', 2*x end)))
a b 0
a b 2
a b 4
a b 6
a b 8
> each(print, take(5, tabulate(function(x) return x^2 end)))
0
1
4
9
16
.. function:: zeros()
:returns: an iterator
The iterator returns ``0`` indefinitely.
Examples:
.. code-block:: lua
> each(print, take(5, zeros()))
0
0
0
0
0
.. function:: ones()
:returns: an iterator
The iterator that returns ``1`` indefinitely.
Example::
> each(print, take(5, ones()))
1
1
1
1
1
Random sampling
---------------
.. function:: rands([n[, m]])
:param n: an endpoint of the interval (see below)
:type n: uint
:param m: an endpoint of the interval (see below)
:type m: uint
:returns: an iterator
The iterator returns random values using :func:`math.random`.
If the **n** and **m** are set then the iterator returns pseudo-random
integers in the ``[n, m)`` interval (i.e. **m** is not included).
If the **m** is not set then the iterator generates pseudo-random integers
in the ``[0, n)`` interval. When called without arguments returns
pseudo-random real numbers with uniform distribution in the
interval ``[0, 1)``.
.. warning:: This iterator is not pure-functional and may not work as
expected with some library functions.
Examples:
.. code-block:: lua
> each(print, take(10, rands(10, 20)))
19
17
11
19
12
13
14
16
10
11
> each(print, take(5, rands(10)))
7
6
5
9
0
> each(print, take(5, rands()))
0.79420629243124
0.69885246563716
0.5901037417281
0.7532286166836
0.080971251199854
|
