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|
-- 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 select, unpack, next = select, unpack, next;
local function pack(...) return { n = select("#", ...), ... }; end
-- 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
-- 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
local 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;
end
-- Skip the first n items an iterator returns
function it.skip(n, f, s, var)
for i=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, var = {};
while true do
var = f(s, var);
if var == nil then break; end
t_insert(t, var);
end
return t;
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
return it;
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