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prosody
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util/iterators.lua @ 5848:06156bfd4eaf
mod_storage_sql2: Add method for deleting items from archives with same syntax as :find()
author | Kim Alvefur <zash@zash.se> |
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date | Sat, 28 Sep 2013 22:04:04 +0200 |
parent | 5776:bd0ff8ae98a8 |
child | 7184:dedc6bf180e2 |
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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 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;