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weak_type.lua
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weak_type.lua
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--[[
mediacircus.type.lua
--]]
local _type, setmetatable, getmetatable, select, ipairs, pairs, tostring, error, assert, print, unpack, fmt =
type, setmetatable, getmetatable, select, ipairs, pairs, tostring, error, assert, print, table.unpack, string.format
-- print(("%s %s %s"):match("%%"))
local have_debug, debug = pcall(require, 'debug')
_ENV = {}
local function get_ud_name(ud)
if not have_debug then return "userdata" end
local ud_mt = getmetatable(ud)
local registry = debug.getregistry()
for i, v in pairs(registry) do
if v == ud_mt then
return i
end
end
end
local type = setmetatable({}, {
__call = function(t, ...)
if select("#", ...) == 1 then
return _type(...)
else
return t.check(...)
end
end
})
local function normalize_to_type(...)
if select("#", ...) ~= 0 then
return type((...), "type") and (...) or type.get((...)), normalize_to_type(select(2,...))
else
return nil
end
end
type.types = setmetatable({}, {
__mode = "v",
__type={types = 1, "types", table = true}}
)
local type_mt = {
__type = {type = 1, "type", table = true},
__call = function(self, o)
return type.cast(o, self)
end,
__tostring = function(self)
return self[1]
end,
__eq = function(a,b)
return type.eq(a,b)
end,
__lt = function(a, b)
return type.le(a,b)
end,
__le = function(a, b)
return type.le(a,b)
end
}
local types = type.types
function type.new(t)
if _type(t) == "string" then
t = {t}
elseif _type(t) ~= "table" then
error("Expected string or table of type names.")
end
local new_type = {}
for i,v in ipairs(t) do
new_type[i] = v
new_type[v] = i
-- print("making",new_type[v],new_type[i])
end
--make a table entry, but don't index it.
--that way #length points to how many types
--are assigned to it, but not the obvious ones.
--also, tables that are passed in can be done this way too.
if t.table or t.table == nil and not t.userdata then -- default path
new_type.table, new_type.userdata = true, false
elseif t.userdata and not t.table then --userdata is true
new_type.table, new_type.userdata = false, true
elseif t.table and t.userdata then--
error("A type can't be a table and a userdata value.")
else --the specified it. probably t.table is false and so is userdata (native type.)
new_type.table, new_type.userdata = t.table, t.userdata
end
types[new_type[1]] = new_type
return setmetatable(new_type, type_mt)
end
function type.get(o)
local obj_type = _type(o)
if obj_type == "table" then
local o_mt = getmetatable(o)
return o_mt and o_mt.__type or types["table"]
elseif have_debug and obj_type == "userdata" then
local ud_name = get_ud_name(o)
if types[ud_name] then
if not types[ud_name].userdata then
error(fmt("Name clash! Previous type with the name '%s' was defined in userspace (not a metatable).",
ud_name),
2)
end
return types[ud_name]
elseif ud_name then
return type.new({ud_name, userdata = true, table = false})
else
return types.userdata --couldn't find it.
end
else
return types[_type(o)] or error(fmt("Undefined type: %s",_type(o)), 2)
end
end
function type.find(type_name)
return types[type_name]
end
function type.check(...)
local arg_len = select("#", ...)
if arg_len == 0 then
return types.undefined[1], types.undefined[2]
elseif arg_len == 1 then
return type.tostring((...))
end
local o_type = type.get((...))
-- o is at one, so skip that. make i 2
for i = 2, arg_len do
local cur_search = (select(i , ...))
if o_type[cur_search] then
return o_type[1], cur_search
end
end
--didn't find it.
return false
end
function type.tostring(o)
return tostring(type.get(o))
end
function type.cast (o, new_type)
if _type(o) ~= "table" then
error("Expected a table as first argument to type.cast. Received %s", _type(o) )
end
local o_mt = getmetatable(o) or {}
--if a string is passed in, and that string is an index of types,
--then they want to cast an existing type.
if _type(t) == "string" and types[new_type] then
o_mt.__type = types[new_type]
--Maybe they're removing the type?
elseif new_type == nil then
o_mt.__type = nil
--Are the placing an existing type?
elseif type.check(new_type, "type") then
o_mt.__type = new_type
--Is it a new type?
else
o_mt.__type = type.new(new_type)
end
return setmetatable(o, o_mt)
end
--this isn't right. if all of the types in a
--are found in b, then it should be true
--so type.le(a,b) and type.le(b, a)?
function type.eq(a, b)
a, b = normalize_to_type(a, b)
return type.le(a,b) and type.le(b, a)
end
function type.lt(a,b)
return type.le(a,b) and not type.le(b, a)
end
-- Does not return true for equality. Only less than.
local function assert_type(o)
if not type(o, "type") then
error(fmt("Error: expected 'type' and received %s", type.tostring(o)),2)
else
return o
end
end
function type.le(a, b)
a,b = normalize_to_type(a,b)
if a[1] == "table" or a[1] == "userdata" then
return b[a[1]] and true or false
--two complex types.
else
for i, v in ipairs(a) do
if not b[v] then
return false
end
end
return true
end
end
type.native = {
type.new({"userdata", table = false, userdata = true}),
type.new({"table", userdata = false}),
type.new({"string", table = false}),
type.new({"number", table = false}),
type.new({"boolean", table = false}),
type.new({"function", table = false}),
type.new({"thread", table = false}),
type.new({"nil", table = false}),
type.new({"undefined", "nil", table = false})
}
return type