Lua util functions - pretty-printing, defaultdict, etc.

Lua snippets

   Just some Lua snippets.

defaultdict.lua

function defaultdict(default_value_factory)
    local mt = {
        __index = function(t, key)
            if not rawget(t, key) then
                rawset(t, key, default_value_factory())
            end
            return rawget(t, key)
        end
    }
    return setmetatable({}, mt)
end

lua52-compat.lua

local function setup_pairs()
    local t = setmetatable({}, {
        __pairs=function(t)
            return pairs({x = 4, y = 6})
        end
    })
    for k,v in pairs(t) do return end

    rawpairs = pairs
    function pairs(t)
        local mt = getmetatable(t)
        return (mt and mt.__pairs or rawpairs)(t)
    end
end

local function setup_ipairs()
    local t = setmetatable({}, {
        __ipairs=function(t)
            return pairs({x = 4, y = 6})
        end
    })
    for k,v in ipairs(t) do return end

    rawipairs = ipairs
    function ipairs(t)
        local mt = getmetatable(t)
        return (mt and mt.__ipairs or rawipairs)(t)
    end
end

setup_pairs()
setup_ipairs()

str.lua

function str(obj, pretty_mode, max_depth, _depth, _visited)
    max_depth = max_depth or -1
    _depth = _depth or 1
    _visited = _visited and setmetatable({}, {__index = _visited}) or {}
    pretty_mode = pretty_mode or false

    local obj_type = type(obj)

    if obj_type == "string" then
        return '"' .. obj .. '"'
    elseif obj_type == "table" and _visited[obj] ~= nil and _visited[obj] ~= _depth then
        return "<loop>"
    elseif obj_type == "table" and (max_depth < 0 or _depth <= max_depth) then
        _visited[obj] = true
        local result = "{"
        if pretty_mode then result = result .. "\n"; end

        local indent = pretty_mode and string.rep("    ", _depth) or ""
        local prev_indent = pretty_mode and string.rep("    ", _depth-1) or ""
        
        for k, v in ipairs(obj) do
            result = result .. indent .. str(v, pretty_mode, max_depth, _depth + 1, _visited) .. ", "
            if pretty_mode then result = result .. "\n"; end
        end
        for k, v in pairs(obj) do
            if type(k) ~= "number" or not (k >= 1 and k <= #obj) then
                result = result .. indent .. tostring(k) .. " = " .. str(v, pretty_mode, max_depth, _depth + 1, _visited) .. ", "
                if pretty_mode then result = result .. "\n"; end
            end
        end
        result = result .. prev_indent .. "}"

        return result
    elseif obj_type == "number" or obj_type == "nil" then
        return tostring(obj)
    elseif obj_type == "boolean" then
        return "[" .. tostring(obj) .. "]"
    else 
        return "<" .. (tostring(obj) or "userdata/unknown") .. ">"
    end
end