prosody
3d17b2bf0e0c
util/iterators.lua

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util/iterators.lua @ 7990:3d17b2bf0e0c

MUC: Shorter label
author Kim Alvefur <zash@zash.se>
date Tue, 21 Mar 2017 04:41:40 +0100
parent 7355:4b4cf0167391
child 8389:5d866eb8f18f
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1 -- Prosody IM
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2 -- Copyright (C) 2008-2010 Matthew Wild
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3 -- Copyright (C) 2008-2010 Waqas Hussain
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4 --
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5 -- This project is MIT/X11 licensed. Please see the
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6 -- COPYING file in the source package for more information.
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7 --
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8
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9 --[[ Iterators ]]--
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10
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11 local it = {};
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12
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13 local t_insert = table.insert;
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14 local select, next = select, next;
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15 local unpack = table.unpack or unpack; --luacheck: ignore 113
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16 local pack = table.pack or function (...) return { n = select("#", ...), ... }; end
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17
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18 -- Reverse an iterator
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19 function it.reverse(f, s, var)
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20 local results = {};
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21
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22 -- First call the normal iterator
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23 while true do
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24 local ret = { f(s, var) };
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25 var = ret[1];
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26 if var == nil then break; end
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27 t_insert(results, 1, ret);
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28 end
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29
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30 -- Then return our reverse one
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31 local i,max = 0, #results;
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32 return function (_results)
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33 if i<max then
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34 i = i + 1;
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35 return unpack(_results[i]);
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36 end
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37 end, results;
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38 end
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39
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40 -- Iterate only over keys in a table
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41 local function _keys_it(t, key)
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42 return (next(t, key));
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43 end
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44 function it.keys(t)
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45 return _keys_it, t;
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46 end
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47
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48 -- Iterate only over values in a table
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49 function it.values(t)
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50 local key, val;
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51 return function (_t)
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52 key, val = next(_t, key);
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53 return val;
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54 end, t;
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55 end
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56
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57 -- Iterate over the n:th return value
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58 function it.select(n, f, s, var)
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59 return function (_s)
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60 local ret = pack(f(_s, var));
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61 var = ret[1];
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62 return ret[n];
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63 end, s, var;
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64 end
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65
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66 -- Given an iterator, iterate only over unique items
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67 function it.unique(f, s, var)
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68 local set = {};
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69
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70 return function ()
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71 while true do
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72 local ret = pack(f(s, var));
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73 var = ret[1];
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74 if var == nil then break; end
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75 if not set[var] then
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76 set[var] = true;
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77 return unpack(ret, 1, ret.n);
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78 end
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79 end
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80 end;
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81 end
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82
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83 --[[ Return the number of items an iterator returns ]]--
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84 function it.count(f, s, var)
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85 local x = 0;
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86
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87 while true do
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88 var = f(s, var);
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89 if var == nil then break; end
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90 x = x + 1;
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91 end
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92
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93 return x;
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94 end
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95
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96 -- Return the first n items an iterator returns
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97 function it.head(n, f, s, var)
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98 local c = 0;
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99 return function (_s, _var)
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100 if c >= n then
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101 return nil;
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102 end
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103 c = c + 1;
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104 return f(_s, _var);
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105 end, s, var;
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106 end
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107
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108 -- Skip the first n items an iterator returns
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109 function it.skip(n, f, s, var)
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110 for _ = 1, n do
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111 var = f(s, var);
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112 end
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113 return f, s, var;
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114 end
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115
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116 -- Return the last n items an iterator returns
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117 function it.tail(n, f, s, var)
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118 local results, count = {}, 0;
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119 while true do
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120 local ret = pack(f(s, var));
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121 var = ret[1];
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122 if var == nil then break; end
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123 results[(count%n)+1] = ret;
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124 count = count + 1;
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125 end
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126
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127 if n > count then n = count; end
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128
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129 local pos = 0;
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130 return function ()
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131 pos = pos + 1;
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132 if pos > n then return nil; end
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133 local ret = results[((count-1+pos)%n)+1];
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134 return unpack(ret, 1, ret.n);
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135 end
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136 --return reverse(head(n, reverse(f, s, var))); -- !
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137 end
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138
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139 function it.filter(filter, f, s, var)
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140 if type(filter) ~= "function" then
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141 local filter_value = filter;
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142 function filter(x) return x ~= filter_value; end
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143 end
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144 return function (_s, _var)
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145 local ret;
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146 repeat ret = pack(f(_s, _var));
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147 _var = ret[1];
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148 until _var == nil or filter(unpack(ret, 1, ret.n));
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149 return unpack(ret, 1, ret.n);
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150 end, s, var;
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151 end
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152
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153 local function _ripairs_iter(t, key) if key > 1 then return key-1, t[key-1]; end end
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154 function it.ripairs(t)
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155 return _ripairs_iter, t, #t+1;
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156 end
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157
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158 local function _range_iter(max, curr) if curr < max then return curr + 1; end end
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159 function it.range(x, y)
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160 if not y then x, y = 1, x; end -- Default to 1..x if y not given
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161 return _range_iter, y, x-1;
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162 end
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163
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164 -- Convert the values returned by an iterator to an array
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165 function it.to_array(f, s, var)
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166 local t = {};
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167 while true do
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168 var = f(s, var);
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169 if var == nil then break; end
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170 t_insert(t, var);
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171 end
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172 return t;
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173 end
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174
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175 -- Treat the return of an iterator as key,value pairs,
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176 -- and build a table
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177 function it.to_table(f, s, var)
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178 local t, var2 = {};
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179 while true do
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180 var, var2 = f(s, var);
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181 if var == nil then break; end
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182 t[var] = var2;
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183 end
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184 return t;
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185 end
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186
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187 return it;