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comparison: iterators.lua
iterators.lua
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| -1:000000000000 | 0:d17a1b659852 |
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| 1 -- Prosody IM | |
| 2 -- Copyright (C) 2008-2010 Matthew Wild | |
| 3 -- Copyright (C) 2008-2010 Waqas Hussain | |
| 4 -- | |
| 5 -- This project is MIT/X11 licensed. Please see the | |
| 6 -- COPYING file in the source package for more information. | |
| 7 -- | |
| 8 | |
| 9 --[[ Iterators ]]-- | |
| 10 | |
| 11 -- Reverse an iterator | |
| 12 function reverse(f, s, var) | |
| 13 local results = {}; | |
| 14 | |
| 15 -- First call the normal iterator | |
| 16 while true do | |
| 17 local ret = { f(s, var) }; | |
| 18 var = ret[1]; | |
| 19 if var == nil then break; end | |
| 20 table.insert(results, 1, ret); | |
| 21 end | |
| 22 | |
| 23 -- Then return our reverse one | |
| 24 local i,max = 0, #results; | |
| 25 return function (results) | |
| 26 if i<max then | |
| 27 i = i + 1; | |
| 28 return unpack(results[i]); | |
| 29 end | |
| 30 end, results; | |
| 31 end | |
| 32 | |
| 33 -- Iterate only over keys in a table | |
| 34 local function _keys_it(t, key) | |
| 35 return (next(t, key)); | |
| 36 end | |
| 37 function keys(t) | |
| 38 return _keys_it, t; | |
| 39 end | |
| 40 | |
| 41 -- Iterate only over values in a table | |
| 42 function values(t) | |
| 43 local key, val; | |
| 44 return function (t) | |
| 45 key, val = next(t, key); | |
| 46 return val; | |
| 47 end, t; | |
| 48 end | |
| 49 | |
| 50 -- Given an iterator, iterate only over unique items | |
| 51 function unique(f, s, var) | |
| 52 local set = {}; | |
| 53 | |
| 54 return function () | |
| 55 while true do | |
| 56 local ret = { f(s, var) }; | |
| 57 var = ret[1]; | |
| 58 if var == nil then break; end | |
| 59 if not set[var] then | |
| 60 set[var] = true; | |
| 61 return var; | |
| 62 end | |
| 63 end | |
| 64 end; | |
| 65 end | |
| 66 | |
| 67 --[[ Return the number of items an iterator returns ]]-- | |
| 68 function count(f, s, var) | |
| 69 local x = 0; | |
| 70 | |
| 71 while true do | |
| 72 local ret = { f(s, var) }; | |
| 73 var = ret[1]; | |
| 74 if var == nil then break; end | |
| 75 x = x + 1; | |
| 76 end | |
| 77 | |
| 78 return x; | |
| 79 end | |
| 80 | |
| 81 -- Return the first n items an iterator returns | |
| 82 function head(n, f, s, var) | |
| 83 local c = 0; | |
| 84 return function (s, var) | |
| 85 if c >= n then | |
| 86 return nil; | |
| 87 end | |
| 88 c = c + 1; | |
| 89 return f(s, var); | |
| 90 end, s; | |
| 91 end | |
| 92 | |
| 93 -- Skip the first n items an iterator returns | |
| 94 function skip(n, f, s, var) | |
| 95 for i=1,n do | |
| 96 var = f(s, var); | |
| 97 end | |
| 98 return f, s, var; | |
| 99 end | |
| 100 | |
| 101 -- Return the last n items an iterator returns | |
| 102 function tail(n, f, s, var) | |
| 103 local results, count = {}, 0; | |
| 104 while true do | |
| 105 local ret = { f(s, var) }; | |
| 106 var = ret[1]; | |
| 107 if var == nil then break; end | |
| 108 results[(count%n)+1] = ret; | |
| 109 count = count + 1; | |
| 110 end | |
| 111 | |
| 112 if n > count then n = count; end | |
| 113 | |
| 114 local pos = 0; | |
| 115 return function () | |
| 116 pos = pos + 1; | |
| 117 if pos > n then return nil; end | |
| 118 return unpack(results[((count-1+pos)%n)+1]); | |
| 119 end | |
| 120 --return reverse(head(n, reverse(f, s, var))); | |
| 121 end | |
| 122 | |
| 123 -- Convert the values returned by an iterator to an array | |
| 124 function it2array(f, s, var) | |
| 125 local t, var = {}; | |
| 126 while true do | |
| 127 var = f(s, var); | |
| 128 if var == nil then break; end | |
| 129 table.insert(t, var); | |
| 130 end | |
| 131 return t; | |
| 132 end | |
| 133 | |
| 134 -- Treat the return of an iterator as key,value pairs, | |
| 135 -- and build a table | |
| 136 function it2table(f, s, var) | |
| 137 local t, var = {}; | |
| 138 while true do | |
| 139 var, var2 = f(s, var); | |
| 140 if var == nil then break; end | |
| 141 t[var] = var2; | |
| 142 end | |
| 143 return t; | |
| 144 end |
