diff --git a/lib_materials_utils.lua b/lib_materials_utils.lua
index b75c066..b2a53c0 100644
--- a/lib_materials_utils.lua
+++ b/lib_materials_utils.lua
@@ -136,6 +136,10 @@ local S = lib_materials.intllib
 
 
 
+-- Push an element onto a stack (table).
+function push(t, x)
+	t[#t+1] = x
+end
 
 
 ----------------------