[spec/*,*] Split library in submodules.

meta.lua

@@ -0,0 +1,38 @@
+--- Functions dealing with metatables and tables merging.
+--
+-- @module gear.meta
+-- @copyright 2022 The DoubleFourteen Code Forge
+-- @author Lorenzo Cogotti
+
+local meta = {}
+
+
+--- Test whether 'obj' is an instance of a given class 'cls'.
+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.
+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
+
+return meta