ChaiScript · lefticus · Apr 15, 2026 · Apr 14, 2026 · Apr 14, 2026 · Apr 14, 2026
diff --git a/cheatsheet.md b/cheatsheet.md
@@ -829,6 +829,94 @@ class My_Class {
 };
 ```
 
+## Strong Typedefs
+
+Strong typedefs create distinct types that are not interchangeable with their underlying type
+or with other typedefs of the same underlying type. They use `Dynamic_Object` internally and
+automatically expose operators that the underlying type supports.
+
+### Basic Usage
+
+```
+using Meters = int
+using Seconds = int
+
+var d = Meters(100)
+var t = Seconds(10)
+
+// d and t are distinct types — you cannot accidentally mix them
+// Meters + Seconds would require an explicit conversion
+```
+
+### Arithmetic and Comparison
+
+Operators from the underlying type are forwarded and remain strongly typed:
+
+```
+using Meters = int
+
+var a = Meters(10)
+var b = Meters(20)
+
+var c = a + b        // Meters(30) — result is still Meters
+var bigger = b > a   // true — comparisons return bool
+
+// Compound assignment operators work too
+a += b               // a is now Meters(30)
+```
+
+### String-Based Strong Typedefs
+
+Strong typedefs work with any type, not just numeric types:
+
+```
+using Name = string
+
+var n = Name("Alice")
+var greeting = Name("Hello, ") + Name("world")  // Name — string concatenation is forwarded
+```
+
+### Accessing the Underlying Value
+
+Use `to_underlying` to extract the wrapped value:
+
+```
+using Meters = int
+
+var d = Meters(42)
+var raw = to_underlying(d)  // 42, plain int
+```
+
+### Extending Strong Typedefs
+
+You can add custom operations to strong typedefs just like any other ChaiScript type:
+
+```
+using Meters = int
+using Seconds = int
+using MetersPerSecond = int
+
+def speed(Meters d, Seconds t) {
+  MetersPerSecond(to_underlying(d) / to_underlying(t))
+}
+
+var s = speed(Meters(100), Seconds(10))  // MetersPerSecond(10)
+```
+
+You can also overload operators between different strong typedefs:
+
+```
+using Meters = int
+using Feet = int
+
+def to_feet(Meters m) {
+  Feet((to_underlying(m) * 328) / 100)
+}
+
+var m = Meters(10)
+var f = to_feet(m)  // Feet(32)
+```
+
 ## method_missing
 
 A function of the signature `method_missing(object, name, param1, param2, param3)` will be called if an appropriate

diff --git a/grammar/chaiscript.ebnf b/grammar/chaiscript.ebnf
@@ -68,6 +68,7 @@ enum_entry           ::= id ( "=" integer )?
 
 underlying_type      ::= id
 
+
 /* ---- Blocks & flow keywords ---- */
 
 block                ::= "{" statements* "}"

diff --git a/include/chaiscript/language/chaiscript_common.hpp b/include/chaiscript/language/chaiscript_common.hpp
@@ -33,7 +33,7 @@ namespace chaiscript {
     template<typename T>
     static bool is_reserved_word(const T &s) noexcept {
       const static std::unordered_set<std::uint32_t>
-          words{utility::hash("def"), utility::hash("fun"), utility::hash("while"), utility::hash("for"), utility::hash("if"), utility::hash("else"), utility::hash("&&"), utility::hash("||"), utility::hash(","), utility::hash("auto"), utility::hash("return"), utility::hash("break"), utility::hash("true"), utility::hash("false"), utility::hash("class"), utility::hash("attr"), utility::hash("var"), utility::hash("global"), utility::hash("GLOBAL"), utility::hash("_"), utility::hash("__LINE__"), utility::hash("__FILE__"), utility::hash("__FUNC__"), utility::hash("__CLASS__"), utility::hash("const"), utility::hash("enum")};
+          words{utility::hash("def"), utility::hash("fun"), utility::hash("while"), utility::hash("for"), utility::hash("if"), utility::hash("else"), utility::hash("&&"), utility::hash("||"), utility::hash(","), utility::hash("auto"), utility::hash("return"), utility::hash("break"), utility::hash("true"), utility::hash("false"), utility::hash("class"), utility::hash("attr"), utility::hash("var"), utility::hash("global"), utility::hash("GLOBAL"), utility::hash("_"), utility::hash("__LINE__"), utility::hash("__FILE__"), utility::hash("__FUNC__"), utility::hash("__CLASS__"), utility::hash("const"), utility::hash("using"), utility::hash("enum")};
 
       return words.count(utility::hash(s)) == 1;
     }
@@ -107,6 +107,7 @@ namespace chaiscript {
     Compiled,
     Const_Var_Decl,
     Const_Assign_Decl,
+    Using,
     Enum,
     Namespace_Block
   };
@@ -129,7 +130,7 @@ namespace chaiscript {
   namespace {
     /// Helper lookup to get the name of each node type
     constexpr const char *ast_node_type_to_string(AST_Node_Type ast_node_type) noexcept {
-      constexpr const char *const ast_node_types[] = {"Id", "Fun_Call", "Unused_Return_Fun_Call", "Arg_List", "Equation", "Var_Decl", "Assign_Decl", "Array_Call", "Dot_Access", "Lambda", "Block", "Scopeless_Block", "Def", "While", "If", "For", "Ranged_For", "Inline_Array", "Inline_Map", "Return", "File", "Prefix", "Break", "Continue", "Map_Pair", "Value_Range", "Inline_Range", "Try", "Catch", "Finally", "Method", "Attr_Decl", "Logical_And", "Logical_Or", "Reference", "Switch", "Case", "Default", "Noop", "Class", "Binary", "Arg", "Global_Decl", "Constant", "Compiled", "Const_Var_Decl", "Const_Assign_Decl", "Enum", "Namespace_Block"};
+      constexpr const char *const ast_node_types[] = {"Id", "Fun_Call", "Unused_Return_Fun_Call", "Arg_List", "Equation", "Var_Decl", "Assign_Decl", "Array_Call", "Dot_Access", "Lambda", "Block", "Scopeless_Block", "Def", "While", "If", "For", "Ranged_For", "Inline_Array", "Inline_Map", "Return", "File", "Prefix", "Break", "Continue", "Map_Pair", "Value_Range", "Inline_Range", "Try", "Catch", "Finally", "Method", "Attr_Decl", "Logical_And", "Logical_Or", "Reference", "Switch", "Case", "Default", "Noop", "Class", "Binary", "Arg", "Global_Decl", "Constant", "Compiled", "Const_Var_Decl", "Const_Assign_Decl", "Using", "Enum", "Namespace_Block"};
 
       return ast_node_types[static_cast<int>(ast_node_type)];
     }
Original file line number	Diff line number	Diff line change
Expand Up		@@ -68,6 +68,7 @@ enum_entry ::= id ( "=" integer )?

		underlying_type ::= id


		/* ---- Blocks & flow keywords ---- */

		block ::= "{" statements* "}"
Expand Down