diff --git a/compiler/compiler.v b/compiler/compiler.v
index 7defe45..6a7c330 100644
--- a/compiler/compiler.v
+++ b/compiler/compiler.v
@@ -49,6 +49,10 @@ const op_apush = u8(36)
 const op_mkstruct = u8(37)
 const op_sget = u8(38)
 const op_sset = u8(39)
+const op_shas = u8(40)
+const op_sdel = u8(41)
+const op_slen = u8(42)
+const op_skeys = u8(43)
 
 // compile parses and compiles VuurRaaf source into an object file.
 pub fn compile(src string) !obj.Obj {
@@ -89,6 +93,7 @@ mut:
 	structs   map[string][]string // declared struct name -> field list
 	enums     map[string][]string // enum name -> variant list
 	enum_vals map[string]int      // 'Enum.variant' -> integer value
+	consts    map[string]i64      // constant name -> integer value
 	local_cnt int
 	argc      int
 	cur_fn    string
@@ -111,6 +116,20 @@ fn gen(prog Program) !obj.Obj {
 			g.enum_vals['${ed.name}.${v}'] = i
 		}
 	}
+	// register constants
+	for cd in prog.consts {
+		if cd.name in g.consts {
+			return error('duplicate constant declaration "${cd.name}"')
+		}
+		// constants must be compile-time integer expressions
+		if cd.value.kind == .int_lit {
+			g.consts[cd.name] = cd.value.int_v
+		} else if cd.value.kind == .bool_lit {
+			g.consts[cd.name] = cd.value.int_v
+		} else {
+			return error('constant "${cd.name}" must be an integer or boolean literal (line ${cd.line})')
+		}
+	}
 	// register struct declarations
 	for sd in prog.structs {
 		if sd.name in g.structs {
@@ -220,10 +239,18 @@ fn (mut g Gen) gen_stmt(st Stmt) ! {
 			g.code << obj.encode_i64(i64(idx))
 		}
 		.index_assign {
-			g.gen_expr(st.base)!
-			g.gen_expr(st.idx)!
-			g.gen_expr(st.expr)!
-			g.code << op_aset
+			// if the index is a string literal, use struct field set (map style)
+			if st.idx.kind == .str_lit {
+				g.gen_expr(st.base)!
+				g.gen_expr(st.expr)!
+				g.emit_field_name(st.idx.str_v)
+				g.code << op_sset
+			} else {
+				g.gen_expr(st.base)!
+				g.gen_expr(st.idx)!
+				g.gen_expr(st.expr)!
+				g.code << op_aset
+			}
 		}
 		.field_assign {
 			// a.b = v  →  a, v, "b"  sset   (field name on top of the stack)
@@ -350,6 +377,11 @@ fn (mut g Gen) gen_stmt(st Stmt) ! {
 			g.emit_label(end_l)
 		}
 		.for_in_stmt {
+			// for x in EnumType { ... }  →  iterate over enum variants as integers
+			if st.expr.kind == .ident && st.expr.name in g.enums {
+				g.gen_for_enum(st.target, st.expr.name, st.body, st.line)!
+				return
+			}
 			// for x in arr  →  idx := 0; while idx < len(arr) { x := arr[idx]; body; idx++ }
 			arr_idx := g.new_local()
 			idx_idx := g.new_local()
@@ -498,6 +530,20 @@ fn (mut g Gen) gen_expr(e Expr) ! {
 		.method_call {
 			// p.dist(x)  →  call <Type>.dist  p, x
 			recv_t := g.method_receiver_type(e)!
+			// built-in: enum.to_string() generates a match on the integer value
+			if e.name == 'to_string' && recv_t in g.enums && e.args.len == 0 {
+				g.gen_enum_to_string(recv_t, *e.left, e.line)!
+				return
+			}
+			// built-in: enum.count() returns the number of variants
+			if e.name == 'count' && recv_t in g.enums && e.args.len == 0 {
+				g.gen_expr(*e.left)!
+				g.code << op_pop
+				variants := g.enums[recv_t]
+				g.code << op_push_i
+				g.code << obj.encode_i64(i64(variants.len))
+				return
+			}
 			g.gen_expr(*e.left)!
 			for a in e.args {
 				g.gen_expr(a)!
@@ -508,17 +554,28 @@ fn (mut g Gen) gen_expr(e Expr) ! {
 			g.code << obj.encode_i64(i64(e.args.len + 1)) // receiver + args
 		}
 		.index {
-			g.gen_expr(*e.left)!
-			g.gen_expr(*e.right)!
-			g.code << op_aget
+			// if the index is a string literal, use struct field access (map style)
+			if e.right.kind == .str_lit {
+				g.gen_expr(*e.left)!
+				g.emit_field_name(e.right.str_v)
+				g.code << op_sget
+			} else {
+				g.gen_expr(*e.left)!
+				g.gen_expr(*e.right)!
+				g.code << op_aget
+			}
 		}
 		.bool_lit {
 			g.code << op_push_i
 			g.code << obj.encode_i64(e.int_v)
 		}
 		.ident {
-			// check if it's an enum variant (e.g., Color.red)
-			if e.name in g.enum_vals {
+			// check if it's a constant
+			if e.name in g.consts {
+				g.code << op_push_i
+				g.code << obj.encode_i64(g.consts[e.name])
+			} else if e.name in g.enum_vals {
+				// check if it's an enum variant (e.g., Color.red)
 				g.code << op_push_i
 				g.code << obj.encode_i64(i64(g.enum_vals[e.name]))
 			} else {
@@ -572,6 +629,32 @@ fn (mut g Gen) gen_call(e Expr) ! {
 		g.code << op_apush
 		return
 	}
+	if e.name == 'has' {
+		if e.args.len != 2 {
+			return error('has() takes exactly two arguments (line ${e.line})')
+		}
+		g.gen_expr(e.args[0])!
+		g.gen_expr(e.args[1])!
+		g.code << op_shas
+		return
+	}
+	if e.name == 'delete' {
+		if e.args.len != 2 {
+			return error('delete() takes exactly two arguments (line ${e.line})')
+		}
+		g.gen_expr(e.args[0])!
+		g.gen_expr(e.args[1])!
+		g.code << op_sdel
+		return
+	}
+	if e.name == 'keys' {
+		if e.args.len != 1 {
+			return error('keys() takes exactly one argument (line ${e.line})')
+		}
+		g.gen_expr(e.args[0])!
+		g.code << op_skeys
+		return
+	}
 	for a in e.args {
 		g.gen_expr(a)!
 	}
@@ -674,7 +757,8 @@ fn (mut g Gen) expr_type(e Expr) string {
 
 // method_receiver_type resolves the struct type a method call is made on.
 // The receiver must be a plain variable whose type the compiler knows
-// (from a typed literal, an assignment, or a method receiver binding).
+// (from a typed literal, an assignment, or a method receiver binding)
+// or an enum variant expression (e.g. Color.red).
 fn (mut g Gen) method_receiver_type(e Expr) !string {
 	recv := e.left
 	if recv.kind == .ident {
@@ -683,9 +767,110 @@ fn (mut g Gen) method_receiver_type(e Expr) !string {
 			return t
 		}
 	}
+	// enum variant: Color.red  →  type is "Color"
+	if recv.kind == .field && recv.left.kind == .ident {
+		key := '${recv.left.name}.${recv.name}'
+		if key in g.enum_vals {
+			return recv.left.name
+		}
+	}
 	return error('cannot resolve method "${e.name}": receiver type unknown (line ${e.line})')
 }
 
+// gen_enum_to_string generates bytecode for `e.to_string()` on an enum value.
+// It emits a match statement that maps each integer variant to its string name.
+fn (mut g Gen) gen_enum_to_string(enum_name string, recv Expr, line int) ! {
+	variants := g.enums[enum_name] or {
+		return error('unknown enum "${enum_name}" at line ${line}')
+	}
+	// store the receiver in a temp local
+	subj_idx := g.new_local()
+	g.gen_expr(recv)!
+	g.emit_store(subj_idx)
+	// end label for the match
+	end_l := g.new_label()
+	for i, v in variants {
+		next_l := g.new_label()
+		// load subject, push variant integer, compare
+		g.emit_load(subj_idx)
+		g.code << op_push_i
+		g.code << obj.encode_i64(i64(i))
+		g.code << op_eq
+		g.code << op_jz
+		g.code << obj.encode_i64(0)
+		g.fixups << Fixup{ name: next_l, off: u32(g.code.len) - 8 }
+		// push the variant name as a string
+		g.code << op_push_s
+		g.code << obj.encode_i64(0)
+		g.relocs << obj.Reloc{ offset: u32(g.code.len) - 8, name: v, kind: 1 }
+		// jump to end
+		g.code << op_jmp
+		g.code << obj.encode_i64(0)
+		g.fixups << Fixup{ name: end_l, off: u32(g.code.len) - 8 }
+		g.emit_label(next_l)
+	}
+	// else: push "unknown"
+	g.code << op_push_s
+	g.code << obj.encode_i64(0)
+	g.relocs << obj.Reloc{ offset: u32(g.code.len) - 8, name: 'unknown', kind: 1 }
+	g.emit_label(end_l)
+}
+
+// gen_for_enum generates a for loop that iterates over all variants of an enum.
+// for x in Color { ... }  →  for i in 0..count { x = i; ... }  (x typed as Color)
+fn (mut g Gen) gen_for_enum(var_name string, enum_name string, body []Stmt, line int) ! {
+	variants := g.enums[enum_name] or {
+		return error('unknown enum "${enum_name}" at line ${line}')
+	}
+	count := variants.len
+	// i := 0
+	var_idx := g.new_local()
+	bound_idx := g.new_local()
+	g.code << op_push_i
+	g.code << obj.encode_i64(0)
+	g.emit_store(var_idx)
+	g.code << op_push_i
+	g.code << obj.encode_i64(i64(count))
+	g.emit_store(bound_idx)
+	loop_l := g.new_label()
+	inc_l := g.new_label()
+	end_l := g.new_label()
+	g.emit_label(loop_l)
+	g.emit_load(var_idx)
+	g.emit_load(bound_idx)
+	g.code << op_lt
+	g.code << op_jz
+	g.code << obj.encode_i64(0)
+	g.fixups << Fixup{ name: end_l, off: u32(g.code.len) - 8 }
+	g.loops << LoopCtx{ break_l: end_l, continue_l: inc_l }
+	prev := g.locals[var_name] or { -1 }
+	prev_t := g.types[var_name] or { '' }
+	g.locals[var_name] = var_idx
+	g.types[var_name] = enum_name // type the loop variable as the enum
+	for s in body {
+		g.gen_stmt(s)!
+	}
+	if prev >= 0 {
+		g.locals[var_name] = prev
+	} else {
+		g.locals.delete(var_name)
+	}
+	if prev_t.len > 0 {
+		g.types[var_name] = prev_t
+	}
+	g.loops.delete_last()
+	g.emit_label(inc_l)
+	g.emit_load(var_idx)
+	g.code << op_push_i
+	g.code << obj.encode_i64(1)
+	g.code << op_add
+	g.emit_store(var_idx)
+	g.code << op_jmp
+	g.code << obj.encode_i64(0)
+	g.fixups << Fixup{ name: loop_l, off: u32(g.code.len) - 8 }
+	g.emit_label(end_l)
+}
+
 // emit_field_name pushes a field name as a string constant. Like string
 // literals it goes through a kind-1 relocation so multi-file links rebase it.
 fn (mut g Gen) emit_field_name(name string) {
diff --git a/compiler/lexer.v b/compiler/lexer.v
index a0834f0..83e9a51 100644
--- a/compiler/lexer.v
+++ b/compiler/lexer.v
@@ -51,6 +51,7 @@ pub enum TokKind {
 	kw_assert
 	kw_import
 	kw_enum
+	kw_const
 }
 
 pub struct Tok {
@@ -278,6 +279,7 @@ fn (mut l Lexer) lex_ident(line int) Tok {
 		'assert' { TokKind.kw_assert }
 		'import' { TokKind.kw_import }
 		'enum' { TokKind.kw_enum }
+		'const' { TokKind.kw_const }
 		else { TokKind.ident }
 	}
 	return Tok{ kind: kind, lit: lit, line: line }
diff --git a/compiler/parser.v b/compiler/parser.v
index b423c6b..ab73caf 100644
--- a/compiler/parser.v
+++ b/compiler/parser.v
@@ -1,10 +1,11 @@
 // parser.v — recursive-descent parser for the VuurRaaf language.
 //
 // Grammar (informal):
-//   program  := import* (struct | enum | fn)*
+//   program  := import* (struct | enum | const | fn)*
 //   import   := 'import' STRING
 //   struct   := 'struct' IDENT '{' [IDENT (',' IDENT)*] '}'
 //   enum     := 'enum' IDENT '{' [IDENT (',' IDENT)*] '}'
+//   const    := 'const' IDENT '=' expr
 //   fn       := 'fn' [ '(' IDENT IDENT ')' ] IDENT '(' [IDENT (',' IDENT)*] ')' block
 //   block    := '{' stmt* '}'
 //   stmt     := 'let' IDENT '=' expr
@@ -145,12 +146,21 @@ pub mut:
 	line     int
 }
 
+// ConstDecl is a `const NAME = value` declaration.
+pub struct ConstDecl {
+pub mut:
+	name  string
+	value Expr
+	line  int
+}
+
 pub struct Program {
 pub mut:
-	fns     []FnDecl
-	structs []StructDecl
-	enums   []EnumDecl
-	imports []ImportDecl
+	fns      []FnDecl
+	structs  []StructDecl
+	enums    []EnumDecl
+	imports  []ImportDecl
+	consts   []ConstDecl
 }
 
 pub fn parse(toks []Tok) !Program {
@@ -209,6 +219,7 @@ fn (mut p Parser) parse_program() !Program {
 		match p.cur().kind {
 			.kw_struct { prog.structs << p.parse_struct_decl()! }
 			.kw_enum { prog.enums << p.parse_enum_decl()! }
+			.kw_const { prog.consts << p.parse_const_decl()! }
 			.kw_fn { prog.fns << p.parse_fn()! }
 			else { return error('unexpected token "${p.cur().lit}" at line ${p.cur().line}') }
 		}
@@ -271,6 +282,15 @@ fn (mut p Parser) parse_enum_decl() !EnumDecl {
 	return EnumDecl{ name: name.lit, variants: variants, line: t.line }
 }
 
+// parse_const_decl parses `const NAME = expr`.
+fn (mut p Parser) parse_const_decl() !ConstDecl {
+	t := p.expect(.kw_const, "'const'")!
+	name := p.expect(.ident, 'constant name')!
+	p.expect(.assign, "'='")!
+	value := p.parse_expr()!
+	return ConstDecl{ name: name.lit, value: value, line: t.line }
+}
+
 // parse_fn parses `fn name(params) { }` or a method `fn (p Type) name(params) { }`.
 fn (mut p Parser) parse_fn() !FnDecl {
 	fn_tok := p.expect(.kw_fn, "'fn'")!
@@ -710,16 +730,22 @@ fn (mut p Parser) parse_args() ![]Expr {
 	return args
 }
 
-// parse_struct_fields parses `{ name: expr, ... }` and returns the fields.
+// parse_struct_fields parses `{ name: expr, ... }` or `{ "key": expr, ... }` and returns the fields.
 fn (mut p Parser) parse_struct_fields() ![]StructField {
 	p.expect(.lbrace, "'{'")!
 	mut fields := []StructField{}
 	if p.cur().kind != .rbrace {
 		for {
-			name := p.expect(.ident, 'field name')!
+			// field name can be an identifier or a string literal (for maps)
+			mut fname := ''
+			if p.cur().kind == .str_lit {
+				fname = p.advance().lit
+			} else {
+				fname = p.expect(.ident, 'field name')!.lit
+			}
 			p.expect(.colon, "':'")!
 			val := p.parse_expr()!
-			fields << StructField{ name: name.lit, val: val }
+			fields << StructField{ name: fname, val: val }
 			if p.cur().kind == .comma {
 				p.advance()
 				continue
@@ -737,5 +763,6 @@ fn (mut p Parser) looks_like_struct_lit() bool {
 	if p.pos + 2 >= p.toks.len {
 		return false
 	}
-	return p.toks[p.pos + 1].kind == .ident && p.toks[p.pos + 2].kind == .colon
+	// typed struct literal: `{ ident :` or map literal: `{ "key" :`
+	return (p.toks[p.pos + 1].kind == .ident || p.toks[p.pos + 1].kind == .str_lit) && p.toks[p.pos + 2].kind == .colon
 }
diff --git a/examples/constants.vr b/examples/constants.vr
new file mode 100644
index 0000000..0bccdb4
--- /dev/null
+++ b/examples/constants.vr
@@ -0,0 +1,50 @@
+// constants.vr — demonstrates const declarations
+
+const MAX_SIZE = 100
+const MIN_VALUE = 0
+const IS_DEBUG = 1
+const VERSION = 42
+
+fn calculate(x) {
+	// constants work inside functions
+	if x > MAX_SIZE {
+		return MAX_SIZE
+	}
+	if x < MIN_VALUE {
+		return MIN_VALUE
+	}
+	return x
+}
+
+fn main() {
+	// constants at top level
+	assert MAX_SIZE == 100
+	assert MIN_VALUE == 0
+	assert IS_DEBUG == 1
+	assert VERSION == 42
+	println("Constants: 100, 0, 1, 42")
+	
+	// constants in expressions
+	let limit = MAX_SIZE * 2
+	assert limit == 200
+	println("MAX_SIZE * 2 = 200")
+	
+	// constants in conditions
+	if IS_DEBUG == 1 {
+		println("Debug mode is ON")
+	}
+	
+	// constants in functions
+	let val = calculate(150)
+	assert val == 100
+	println("calculate(150) = 100")
+	
+	let val2 = calculate(-5)
+	assert val2 == 0
+	println("calculate(-5) = 0")
+	
+	// constants with boolean operations
+	assert MAX_SIZE > MIN_VALUE
+	assert VERSION == 42
+	println("All constant assertions passed!")
+}
diff --git a/examples/enum_count.vr b/examples/enum_count.vr
new file mode 100644
index 0000000..00e56a1
--- /dev/null
+++ b/examples/enum_count.vr
@@ -0,0 +1,46 @@
+// enum_count.vr — demonstrates built-in enum.count()
+
+enum Color {
+	red
+	green
+	blue
+}
+
+enum Day {
+	monday
+	tuesday
+	wednesday
+	thursday
+	friday
+	saturday
+	sunday
+}
+
+enum Coin {
+	penny
+	nickel
+	dime
+	quarter
+}
+
+fn main() {
+	// Color.count() = 3
+	let c = Color.red
+	assert c.count() == 3
+	println("Color has 3 variants")
+	
+	// Day.count() = 7
+	assert Day.monday.count() == 7
+	println("Day has 7 variants")
+	
+	// Coin.count() = 4
+	let coin = Coin.dime
+	assert coin.count() == 4
+	println("Coin has 4 variants")
+	
+	// on a variant literal directly
+	assert Color.blue.count() == 3
+	println("Color.blue.count() = 3")
+	
+	println("All count assertions passed!")
+}
diff --git a/examples/enum_iter.vr b/examples/enum_iter.vr
new file mode 100644
index 0000000..7558673
--- /dev/null
+++ b/examples/enum_iter.vr
@@ -0,0 +1,64 @@
+// enum_iter.vr — demonstrates for-in over enum types
+
+enum Color {
+	red
+	green
+	blue
+}
+
+enum Day {
+	monday
+	tuesday
+	wednesday
+	thursday
+	friday
+	saturday
+	sunday
+}
+
+fn main() {
+	// iterate over Color variants
+	println("Colors:")
+	for c in Color {
+		print("  ")
+		println(c.to_string())
+	}
+	
+	// iterate and use count
+	let total = 0
+	for c in Color {
+		total = total + c.count()
+	}
+	assert total == 9 // 3 + 3 + 3
+	println("Sum of counts: 9")
+	
+	// iterate and use to_string in a match
+	for d in Day {
+		if d == Day.saturday or d == Day.sunday {
+			println(d.to_string() + " is weekend")
+		}
+	}
+	
+	// break and continue work
+	let weekdays = 0
+	for d in Day {
+		if d == Day.saturday {
+			break
+		}
+		weekdays = weekdays + 1
+	}
+	assert weekdays == 5
+	println("Weekday count: 5")
+	
+	// collect variant indices
+	let indices = []
+	for c in Color {
+		push(indices, c)
+	}
+	assert indices[0] == 0
+	assert indices[1] == 1
+	assert indices[2] == 2
+	println("Indices: 0, 1, 2")
+	
+	println("All enum iteration assertions passed!")
+}
diff --git a/examples/enum_tostring.vr b/examples/enum_tostring.vr
new file mode 100644
index 0000000..ff6df78
--- /dev/null
+++ b/examples/enum_tostring.vr
@@ -0,0 +1,50 @@
+// enum_tostring.vr — demonstrates built-in enum.to_string()
+
+enum Color {
+	red
+	green
+	blue
+}
+
+enum Day {
+	monday
+	tuesday
+	wednesday
+	thursday
+	friday
+	saturday
+	sunday
+}
+
+fn main() {
+	// Color.to_string()
+	let c = Color.red
+	println(c.to_string())
+	assert c.to_string() == "red"
+	
+	let g = Color.green
+	println(g.to_string())
+	assert g.to_string() == "green"
+	
+	let b = Color.blue
+	println(b.to_string())
+	assert b.to_string() == "blue"
+	
+	// Day.to_string()
+	let d = Day.friday
+	println(d.to_string())
+	assert d.to_string() == "friday"
+	
+	let sun = Day.sunday
+	println(sun.to_string())
+	assert sun.to_string() == "sunday"
+	
+	// enum variant literal .to_string()
+	println(Color.green.to_string())
+	assert Color.green.to_string() == "green"
+	
+	println(Day.monday.to_string())
+	assert Day.monday.to_string() == "monday"
+	
+	println("All to_string assertions passed!")
+}
diff --git a/examples/maps.vr b/examples/maps.vr
new file mode 100644
index 0000000..4623079
--- /dev/null
+++ b/examples/maps.vr
@@ -0,0 +1,62 @@
+// maps.vr — demonstrates map/dictionary features
+
+fn main() {
+	// create a map using struct literal syntax
+	let person = { "name": "alice", "age": 30 }
+	
+	// access with string index
+	assert person["name"] == "alice"
+	assert person["age"] == 30
+	println("person[\"name\"] = alice")
+	println("person[\"age\"] = 30")
+	
+	// update with string index
+	person["age"] = 31
+	assert person["age"] == 31
+	println("person[\"age\"] after update = 31")
+	
+	// add new keys dynamically
+	person["city"] = "nyc"
+	assert person["city"] == "nyc"
+	println("person[\"city\"] = nyc")
+	
+	// check key existence with has()
+	assert has(person, "name") == 1
+	assert has(person, "missing") == 0
+	println("has(person, \"name\") = 1")
+	println("has(person, \"missing\") = 0")
+	
+	// get all keys with keys()
+	let k = keys(person)
+	assert len(k) == 3
+	println("keys count = 3")
+	
+	// delete a key
+	delete(person, "city")
+	assert has(person, "city") == 0
+	assert len(person) == 2
+	println("after delete: len = 2")
+	
+	// len() works on maps
+	let scores = { "math": 95, "english": 88 }
+	assert len(scores) == 2
+	println("scores len = 2")
+	
+	// nested maps
+	let data = { "user": { "name": "bob" } }
+	assert data["user"]["name"] == "bob"
+	println("nested access = bob")
+	
+	// maps in arrays
+	let users = [{ "name": "a" }, { "name": "b" }]
+	assert users[0]["name"] == "a"
+	assert users[1]["name"] == "b"
+	println("maps in arrays OK")
+	
+	// empty map
+	let empty = {}
+	assert len(empty) == 0
+	println("empty map len = 0")
+	
+	println("All map assertions passed!")
+}
diff --git a/examples/maps_debug.vr b/examples/maps_debug.vr
new file mode 100644
index 0000000..9c59632
--- /dev/null
+++ b/examples/maps_debug.vr
@@ -0,0 +1,19 @@
+// maps_debug.vr — debug map keys function
+
+fn main() {
+	let person = { "name": "alice", "age": 30 }
+	
+	let k = keys(person)
+	let n = len(k)
+	println("len(k) = 2")
+	
+	if n > 0 {
+		println("key0")
+	}
+	if n > 1 {
+		println("key1")
+	}
+	
+	assert n == 2
+	println("keys OK")
+}
diff --git a/vm/vm.v b/vm/vm.v
index 8c710d7..b94ce58 100644
--- a/vm/vm.v
+++ b/vm/vm.v
@@ -56,6 +56,10 @@ const op_apush = u8(36)
 const op_mkstruct = u8(37)
 const op_sget = u8(38)
 const op_sset = u8(39)
+const op_shas = u8(40)  // has(map, "key") -> 1 if key exists, 0 otherwise
+const op_sdel = u8(41)  // delete(map, "key") -> removes the key
+const op_slen = u8(42)  // slen(struct) -> number of fields
+const op_skeys = u8(43) // skeys(struct) -> array of field name strings
 
 const stack_cap = 65536
 
@@ -350,10 +354,13 @@ fn (mut v Vm) exec() ! {
 			op_alen {
 				v.ip++
 				h := v.pop()!
-				if !v.is_arr(h) || !v.valid_arr_handle(h) {
-					return error('len() on a non-array value')
+				if v.is_arr(h) && v.valid_arr_handle(h) {
+					v.push(v.enc_int(i64(v.arrays[v.hand(h)].len)))!
+				} else if v.is_struct(h) && v.valid_struct_handle(h) {
+					v.push(v.enc_int(i64(v.structs[v.hand(h)].fields.len)))!
+				} else {
+					return error('len() on a non-array, non-struct value')
 				}
-				v.push(v.enc_int(i64(v.arrays[v.hand(h)].len)))!
 			}
 			op_apush {
 				v.ip++
@@ -433,6 +440,18 @@ fn (mut v Vm) exec() ! {
 				}
 				v.structs[v.hand(h)] = s
 			}
+			op_shas {
+				v.op_shas()!
+			}
+			op_sdel {
+				v.op_sdel()!
+			}
+			op_slen {
+				v.op_slen()!
+			}
+			op_skeys {
+				v.op_skeys()!
+			}
 			else {
 				return error('unknown opcode ${op} at ip ${v.ip}')
 			}
@@ -440,6 +459,82 @@ fn (mut v Vm) exec() ! {
 	}
 }
 
+// op_shas checks if a struct has a field with the given name.
+// stack: struct, "key"  →  pushes 1 if found, 0 if not.
+fn (mut v Vm) op_shas() ! {
+	v.ip++
+	name := v.pop()!
+	h := v.pop()!
+	if !v.is_struct(h) || !v.valid_struct_handle(h) {
+		return error('has() on a non-struct value')
+	}
+	if !v.is_str(name) || !v.valid_handle(name) {
+		return error('internal: field name is not a string')
+	}
+	fname := v.strings[v.hand(name)]
+	mut found := false
+	for f in v.structs[v.hand(h)].fields {
+		if f.name == fname {
+			found = true
+			break
+		}
+	}
+	v.push(v.enc_int(if found { 1 } else { 0 }))!
+}
+
+// op_sdel removes a field from a struct.
+// stack: struct, "key"  →  pushes the struct handle back.
+fn (mut v Vm) op_sdel() ! {
+	v.ip++
+	name := v.pop()!
+	h := v.pop()!
+	if !v.is_struct(h) || !v.valid_struct_handle(h) {
+		return error('delete() on a non-struct value')
+	}
+	if !v.is_str(name) || !v.valid_handle(name) {
+		return error('internal: field name is not a string')
+	}
+	fname := v.strings[v.hand(name)]
+	mut s := v.structs[v.hand(h)]
+	mut new_fields := []Field{}
+	for f in s.fields {
+		if f.name != fname {
+			new_fields << f
+		}
+	}
+	s.fields = new_fields
+	v.structs[v.hand(h)] = s
+	v.push(h)!
+}
+
+// op_slen returns the number of fields in a struct.
+// stack: struct  →  pushes field count.
+fn (mut v Vm) op_slen() ! {
+	v.ip++
+	h := v.pop()!
+	if !v.is_struct(h) || !v.valid_struct_handle(h) {
+		return error('len() on a non-struct value')
+	}
+	v.push(v.enc_int(i64(v.structs[v.hand(h)].fields.len)))!
+}
+
+// op_skeys returns an array of field name strings.
+// stack: struct  →  pushes array handle.
+fn (mut v Vm) op_skeys() ! {
+	v.ip++
+	h := v.pop()!
+	if !v.is_struct(h) || !v.valid_struct_handle(h) {
+		return error('keys() on a non-struct value')
+	}
+	mut arr := []i64{}
+	for f in v.structs[v.hand(h)].fields {
+		v.strings << f.name
+		arr << v.mkstr(v.strings.len - 1)
+	}
+	v.arrays << arr
+	v.push(v.mkarr(v.arrays.len - 1))!
+}
+
 fn (mut v Vm) read_i64() i64 {
 	mut val := u64(0)
 	for i in 0..8 {
@@ -757,6 +852,10 @@ fn (mut v Vm) trace_op(op u8) {
 		op_mkstruct { 'mkstruct' }
 		op_sget { 'sget' }
 		op_sset { 'sset' }
+		op_shas { 'shas' }
+		op_sdel { 'sdel' }
+		op_slen { 'slen' }
+		op_skeys { 'skeys' }
 		else { '??' }
 	}
 	mut s := ''