-- 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