local qtable = {}

function qtable.map(t, f)
    local nt = {}
    for k,v in pairs(t) do
        nt[k] = f(v)
    end
    return nt
end

function qtable.filter(t, f, dict)
    local nt = {}
    for k,v in pairs(t) do
        if not f(v) then goto continue end
        if dict then
            nt[k] = v
        else
            table.insert(nt, v)
        end
        ::continue::
    end
    return nt
end

-- This is taken from http://lua-users.org/wiki/SortedIteration
-- This version is stripped of comments and empty lines + some stuff is renamed

local function __gen_oindex(t)
    local oindex = {}
    for key in pairs(t) do
        table.insert(oindex, key)
    end
    table.sort(oindex)
    return oindex
end

function qtable.onext(t, state)
    local key = nil
    if state == nil then
        t.__oindex = __gen_oindex(t)
        key = t.__oindex[1]
    else
        for i = 1,#t.__oindex do
            if t.__oindex[i] == state then
                key = t.__oindex[i+1]
            end
        end
    end
    if key then
        return key, t[key]
    end
    t.__oindex = nil
end

function qtable.opairs(t)
    return qtable.onext, t, nil
end

return qtable