prosody
c9b91ddc9c11
util/iterators.lua

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util/iterators.lua @ 4545:c9b91ddc9c11

util.iterators: Make a standard library (no longer injects into global namespace)
author Matthew Wild <mwild1@gmail.com>
date Mon, 23 Jan 2012 00:00:10 +0000
parent 4441:a01b7207cb37
child 5468:2660407c3b73
comparison
equal deleted inserted replaced
4544:316e2b09a562 4545:c9b91ddc9c11
6 -- COPYING file in the source package for more information. 6 -- COPYING file in the source package for more information.
7 -- 7 --
8 8
9 --[[ Iterators ]]-- 9 --[[ Iterators ]]--
10 10
11 local it = {};
12
11 -- Reverse an iterator 13 -- Reverse an iterator
12 function reverse(f, s, var) 14 function it.reverse(f, s, var)
13 local results = {}; 15 local results = {};
14 16
15 -- First call the normal iterator 17 -- First call the normal iterator
16 while true do 18 while true do
17 local ret = { f(s, var) }; 19 local ret = { f(s, var) };
32 34
33 -- Iterate only over keys in a table 35 -- Iterate only over keys in a table
34 local function _keys_it(t, key) 36 local function _keys_it(t, key)
35 return (next(t, key)); 37 return (next(t, key));
36 end 38 end
37 function keys(t) 39 function it.keys(t)
38 return _keys_it, t; 40 return _keys_it, t;
39 end 41 end
40 42
41 -- Iterate only over values in a table 43 -- Iterate only over values in a table
42 function values(t) 44 function it.values(t)
43 local key, val; 45 local key, val;
44 return function (t) 46 return function (t)
45 key, val = next(t, key); 47 key, val = next(t, key);
46 return val; 48 return val;
47 end, t; 49 end, t;
48 end 50 end
49 51
50 -- Given an iterator, iterate only over unique items 52 -- Given an iterator, iterate only over unique items
51 function unique(f, s, var) 53 function it.unique(f, s, var)
52 local set = {}; 54 local set = {};
53 55
54 return function () 56 return function ()
55 while true do 57 while true do
56 local ret = { f(s, var) }; 58 local ret = { f(s, var) };
63 end 65 end
64 end; 66 end;
65 end 67 end
66 68
67 --[[ Return the number of items an iterator returns ]]-- 69 --[[ Return the number of items an iterator returns ]]--
68 function count(f, s, var) 70 function it.count(f, s, var)
69 local x = 0; 71 local x = 0;
70 72
71 while true do 73 while true do
72 local ret = { f(s, var) }; 74 local ret = { f(s, var) };
73 var = ret[1]; 75 var = ret[1];
77 79
78 return x; 80 return x;
79 end 81 end
80 82
81 -- Return the first n items an iterator returns 83 -- Return the first n items an iterator returns
82 function head(n, f, s, var) 84 function it.head(n, f, s, var)
83 local c = 0; 85 local c = 0;
84 return function (s, var) 86 return function (s, var)
85 if c >= n then 87 if c >= n then
86 return nil; 88 return nil;
87 end 89 end
89 return f(s, var); 91 return f(s, var);
90 end, s; 92 end, s;
91 end 93 end
92 94
93 -- Skip the first n items an iterator returns 95 -- Skip the first n items an iterator returns
94 function skip(n, f, s, var) 96 function it.skip(n, f, s, var)
95 for i=1,n do 97 for i=1,n do
96 var = f(s, var); 98 var = f(s, var);
97 end 99 end
98 return f, s, var; 100 return f, s, var;
99 end 101 end
100 102
101 -- Return the last n items an iterator returns 103 -- Return the last n items an iterator returns
102 function tail(n, f, s, var) 104 function it.tail(n, f, s, var)
103 local results, count = {}, 0; 105 local results, count = {}, 0;
104 while true do 106 while true do
105 local ret = { f(s, var) }; 107 local ret = { f(s, var) };
106 var = ret[1]; 108 var = ret[1];
107 if var == nil then break; end 109 if var == nil then break; end
119 end 121 end
120 --return reverse(head(n, reverse(f, s, var))); 122 --return reverse(head(n, reverse(f, s, var)));
121 end 123 end
122 124
123 local function _range_iter(max, curr) if curr < max then return curr + 1; end end 125 local function _range_iter(max, curr) if curr < max then return curr + 1; end end
124 function range(x, y) 126 function it.range(x, y)
125 if not y then x, y = 1, x; end -- Default to 1..x if y not given 127 if not y then x, y = 1, x; end -- Default to 1..x if y not given
126 return _range_iter, y, x-1; 128 return _range_iter, y, x-1;
127 end 129 end
128 130
129 -- Convert the values returned by an iterator to an array 131 -- Convert the values returned by an iterator to an array
130 function it2array(f, s, var) 132 function it.to_array(f, s, var)
131 local t, var = {}; 133 local t, var = {};
132 while true do 134 while true do
133 var = f(s, var); 135 var = f(s, var);
134 if var == nil then break; end 136 if var == nil then break; end
135 table.insert(t, var); 137 table.insert(t, var);
137 return t; 139 return t;
138 end 140 end
139 141
140 -- Treat the return of an iterator as key,value pairs, 142 -- Treat the return of an iterator as key,value pairs,
141 -- and build a table 143 -- and build a table
142 function it2table(f, s, var) 144 function it.to_table(f, s, var)
143 local t, var2 = {}; 145 local t, var2 = {};
144 while true do 146 while true do
145 var, var2 = f(s, var); 147 var, var2 = f(s, var);
146 if var == nil then break; end 148 if var == nil then break; end
147 t[var] = var2; 149 t[var] = var2;
148 end 150 end
149 return t; 151 return t;
150 end 152 end
151 153
154 return it;