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Lua

--- Tables and metatables general utility algorithms.
--
-- @module gear.meta
-- @copyright 2022 The DoubleFourteen Code Forge
-- @author Lorenzo Cogotti
local meta = {}
--- Test whether 'obj' is an instance of the given class 'cls'.
--
-- @tparam table obj
-- @tparam table cls
-- @treturn bool
function meta.isinstance(obj, cls)
repeat
local m = getmetatable(obj)
if m == cls then return true end
obj = m
until obj == nil
return false
end
--- Merge table 'from' into table 'to'.
--
-- For every field in 'from', copy it to destination
-- table 'to', whenever the same field is nil in that table.
--
-- The same process is applied recursively to sub-tables.
--
-- @tparam table to table to merge into
-- @tparam table from table to merge from
-- @treturn table destination table (a reference to 'to')
function meta.mergetable(to, from)
for k,v in pairs(from) do
if to[k] == nil then
to[k] = type(v) == 'table' and meta.mergetable({}, v) or v
end
end
return to
end
--- Table deep copy.
--
-- Copy table 'obj', cloning any sub-table.
-- Handles cyclic references.
--
-- @tparam table obj object to be copied
-- @tparam[opt={}] table copied known copied sub-object table
-- @treturn table newly created clone of 'obj'
function meta.deepcopy(obj, copied)
copied = copied or {}
local r = {}
copied[obj] = r
for k,v in pairs(obj) do
if type(v) == 'table' then
local t = copied[v] or meta.deepcopy(v, copied)
copied[v] = t -- NOP if object was already copied
v = t
end
r[k] = v
end
return r
end
return meta