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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 ]]--
-- Reverse an iterator
function 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
table.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 keys(t)
return _keys_it, t;
end
-- Iterate only over values in a table
function 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 unique(f, s, var)
local set = {};
return function ()
while true do
local ret = { f(s, var) };
var = ret[1];
if var == nil then break; end
if not set[var] then
set[var] = true;
return var;
end
end
end;
end
--[[ Return the number of items an iterator returns ]]--
function count(f, s, var)
local x = 0;
while true do
local ret = { f(s, var) };
var = ret[1];
if var == nil then break; end
x = x + 1;
end
return x;
end
-- Return the first n items an iterator returns
function 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 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 tail(n, f, s, var)
local results, count = {}, 0;
while true do
local ret = { 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
return unpack(results[((count-1+pos)%n)+1]);
end
--return reverse(head(n, reverse(f, s, var)));
end
-- Convert the values returned by an iterator to an array
function it2array(f, s, var)
local t, var = {};
while true do
var = f(s, var);
if var == nil then break; end
table.insert(t, var);
end
return t;
end
-- Treat the return of an iterator as key,value pairs,
-- and build a table
function it2table(f, s, var)
local t, var = {};
while true do
var, var2 = f(s, var);
if var == nil then break; end
t[var] = var2;
end
return t;
end
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