aboutsummaryrefslogtreecommitdiffstats
path: root/util/iterators.lua
blob: 4529697a2fce2baf7cf5f6338560967271a32251 (plain)
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
-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

--[[ Iterators ]]--

local it = {};

local t_insert = table.insert;
local next = next;
local unpack = table.unpack;
local pack = table.pack;
local type = type;
local table, setmetatable = table, setmetatable;

local _ENV = nil;
--luacheck: std none

-- Reverse an iterator
function it.reverse(f, s, var)
	local results = {};

	-- First call the normal iterator
	while true do
		local ret = { f(s, var) };
		var = ret[1];
		if var == nil then break; end
		t_insert(results, 1, ret);
	end

	-- Then return our reverse one
	local i,max = 0, #results;
	return function (_results)
		if i<max then
			i = i + 1;
			return unpack(_results[i]);
		end
	end, results;
end

-- Iterate only over keys in a table
local function _keys_it(t, key)
	return (next(t, key));
end
function it.keys(t)
	return _keys_it, t;
end

-- Iterate only over values in a table
function it.values(t)
	local key, val;
	return function (_t)
		key, val = next(_t, key);
		return val;
	end, t;
end

-- Iterate over the n:th return value
function it.select(n, f, s, var)
	return function (_s)
		local ret = pack(f(_s, var));
		var = ret[1];
		return ret[n];
	end, s, var;
end

-- Given an iterator, iterate only over unique items
function it.unique(f, s, var)
	local set = {};

	return function ()
		while true do
			local ret = pack(f(s, var));
			var = ret[1];
			if var == nil then break; end
			if not set[var] then
				set[var] = true;
				return unpack(ret, 1, ret.n);
			end
		end
	end;
end

--[[ Return the number of items an iterator returns ]]--
function it.count(f, s, var)
	local x = 0;

	while true do
		var = f(s, var);
		if var == nil then break; end
		x = x + 1;
	end

	return x;
end

-- Return the first n items an iterator returns
function it.head(n, f, s, var)
	local c = 0;
	return function (_s, _var)
		if c >= n then
			return nil;
		end
		c = c + 1;
		return f(_s, _var);
	end, s, var;
end

-- Skip the first n items an iterator returns
function it.skip(n, f, s, var)
	for _ = 1, n do
		var = f(s, var);
	end
	return f, s, var;
end

-- Return the last n items an iterator returns
function it.tail(n, f, s, var)
	local results, count = {}, 0;
	while true do
		local ret = pack(f(s, var));
		var = ret[1];
		if var == nil then break; end
		results[(count%n)+1] = ret;
		count = count + 1;
	end

	if n > count then n = count; end

	local pos = 0;
	return function ()
		pos = pos + 1;
		if pos > n then return nil; end
		local ret = results[((count-1+pos)%n)+1];
		return unpack(ret, 1, ret.n);
	end
	--return reverse(head(n, reverse(f, s, var))); -- !
end

function it.filter(filter, f, s, var)
	if type(filter) ~= "function" then
		local filter_value = filter;
		function filter(x) return x ~= filter_value; end
	end
	return function (_s, _var)
		local ret;
		repeat ret = pack(f(_s, _var));
			_var = ret[1];
		until _var == nil or filter(unpack(ret, 1, ret.n));
		return unpack(ret, 1, ret.n);
	end, s, var;
end

local function _ripairs_iter(t, key) if key > 1 then return key-1, t[key-1]; end end
function it.ripairs(t)
	return _ripairs_iter, t, #t+1;
end

local function _range_iter(max, curr) if curr < max then return curr + 1; end end
function it.range(x, y)
	if not y then x, y = 1, x; end -- Default to 1..x if y not given
	return _range_iter, y, x-1;
end

-- Convert the values returned by an iterator to an array
function it.to_array(f, s, var)
	local t = {};
	while true do
		var = f(s, var);
		if var == nil then break; end
		t_insert(t, var);
	end
	return t;
end

function it.sorted_pairs(t, sort_func)
	local keys = it.to_array(it.keys(t));
	table.sort(keys, sort_func);
	local i = 0;
	return function ()
		i = i + 1;
		local key = keys[i];
		if key ~= nil then
			return key, t[key];
		end
	end;
end

-- Treat the return of an iterator as key,value pairs,
-- and build a table
function it.to_table(f, s, var)
	local t, var2 = {};
	while true do
		var, var2 = f(s, var);
		if var == nil then break; end
		t[var] = var2;
	end
	return t;
end

local function _join_iter(j_s, j_var)
	local iterators, current_idx = j_s[1], j_s[2];
	local f, s, var = unpack(iterators[current_idx], 1, 3);
	if j_var ~= nil then
		var = j_var;
	end
	local ret = pack(f(s, var));
	local var1 = ret[1];
	if var1 == nil then
		-- End of this iterator, advance to next
		if current_idx == #iterators then
			-- No more iterators, return nil
			return;
		end
		j_s[2] = current_idx + 1;
		return _join_iter(j_s);
	end
	return unpack(ret, 1, ret.n);
end
local join_methods = {};
local join_mt = {
	__index = join_methods;
	__call = function (t, s, var) --luacheck: ignore 212/t
		return _join_iter(s, var);
	end;
};

function join_methods:append(f, s, var)
	table.insert(self, { f, s, var });
	return self, { self, 1 };
end

function join_methods:prepend(f, s, var)
	table.insert(self, { f, s, var }, 1);
	return self, { self, 1 };
end

function it.join(f, s, var)
	return setmetatable({ {f, s, var} }, join_mt);
end

return it;