diff --git a/generator.v b/generator.v
index 5e78dc0..7d28ac7 100644
--- a/generator.v
+++ b/generator.v
@@ -24,6 +24,7 @@ fn mangle_struct(name string) string {
 
 
 fn get_type_format(type string) string {
+	dump(type)
 	return match type {
 		'int', 'bool' {'d'}
 		'real'        {'f'}
@@ -46,7 +47,7 @@ fn (mut g Generator) get_c_type(typ string) string {
 	return match typ {
 		'real' {'float'}
 		'int' {'int32_t'}
-		'string' {'char*'}
+		'string' {'OneString'}
 		else {typ}
 	}
 }
@@ -70,12 +71,16 @@ fn (mut g Generator) gen_class_print_func(stmt ClassDecl) {
     g.out.writeln('for(int i=0; i<indent + 1; i++) printf("  ");')
     g.out.write_string('printf("${member.name}: ");')
 
-		if g.symbols.lookup_class(member.type) != none {
+		if member.type != 'string' && g.symbols.lookup_class(member.type) != none {
       inner_struct_name := mangle_struct(member.type)
       g.out.writeln('print_${inner_struct_name}(s.${member.name}, indent + 1);')
     } else {
       format := get_type_format(member.type)
-      g.out.writeln('printf("%${format}\\n", s.${member.name});')
+      g.out.write_string('printf("%${format}\\n", s.${member.name}')
+			if member.type == 'string' {
+      	g.out.write_string('.string')
+			}
+      g.out.writeln(');')
     }
   }
 
@@ -168,7 +173,7 @@ fn (mut g Generator) gen_expr(expr Expr) {
 			g.out.write_string(expr.val.str())
 		}
 		StringLiteral {
-			g.out.write_string('\"${expr.val}\"')
+			g.out.write_string('(OneString){\"${expr.val}\", ${expr.val.len}}')
 		}
 		Variable {
 			g.out.write_string(mangle_var(expr.name))
@@ -188,16 +193,20 @@ fn (mut g Generator) gen_expr(expr Expr) {
 			for i < expr.exprs.len {
 				inner_expr := expr.exprs[i];
 				expr_type := expr.types[i];
-				if g.symbols.lookup_class(expr_type) != none {
+				if expr_type != 'string' && g.symbols.lookup_class(expr_type) != none {
 					class_name := mangle_struct(expr_type)
 					g.out.write_string('print_${class_name}(')
 					g.gen_expr(inner_expr)
 					g.out.write_string(', 0);')
+				} else {
 					g.out.write_string('printf(\"')
 					format := get_type_format(expr_type)
 					g.out.write_string('%${format}')
 					g.out.write_string('\", ')
 					g.gen_expr(inner_expr)
+					if expr_type == 'string' {
+						g.out.write_string('.string')
+					}
 					g.out.write_string(');')
 				}
 				i++;
@@ -254,7 +263,7 @@ fn (mut g Generator) gen_c(program []Stmt) string {
 	g.out.writeln('#include <stdio.h>')
 	g.out.writeln('#include <stdbool.h>')
 	g.out.writeln('#include <stdint.h>')
-	//g.out.writeln('typedef struct __one_string_builtin__ {\nchar* string;\nint len;\n} string;')
+	g.out.writeln('typedef struct {\nchar* string;\nint len;\n} OneString;')
 	for stmt in program {
 		g.gen_stmt(stmt)
 	}
diff --git a/lexer.v b/lexer.v
index 944ec05..a8133f8 100644
--- a/lexer.v
+++ b/lexer.v
@@ -5,6 +5,7 @@ import term
 enum TokenType as u8 {
 	kw_let
 	kw_const
+	kw_immutable
 	type
 	kw_if
 	kw_else
@@ -108,6 +109,7 @@ fn toktype_from_kw(kw string) TokenType {
 		'true', 'false' {.boolean}
 		'print' {.kw_print}
 		'class' {.kw_class}
+		'immutable' {.kw_immutable}
 		else {.unknown}
 	}
 }
@@ -127,7 +129,7 @@ fn is_real(str string) bool {
 
 fn is_keyword(str string) bool {
 	return [
-		"void", "int", "real", "bool", "string", "if", "else", "elif", "for", "break", "fn", "return", "let", "const", "true", "false", "print", "class"
+		"void", "int", "real", "bool", "string", "if", "else", "elif", "for", "break", "fn", "return", "let", "const", "true", "false", "print", "class", "immutable"
 	].contains(str)
 }
 
diff --git a/one b/one
index 775aea3..bc63d64 100755
Binary files a/one and b/one differ
diff --git a/parser.v b/parser.v
index 505d322..87fd000 100644
--- a/parser.v
+++ b/parser.v
@@ -32,6 +32,7 @@ type SymbolInfo = VarSymbolInfo | FuncSymbolInfo | ClassSymbolInfo
 
 struct VarSymbolInfo {
 	type string
+	is_immutable bool
 }
 
 struct FuncSymbolInfo {
@@ -96,7 +97,10 @@ fn (mut s SymbolTable) lookup_func(name string) ?FuncSymbolInfo {
 fn (mut s SymbolTable) define_class(name string, members []ClassMember) {
 	mut members_info := map[string]VarSymbolInfo{}
 	for member in members {
-		members_info[member.name] = VarSymbolInfo{member.type}
+		members_info[member.name] = VarSymbolInfo{
+			type: member.type,
+			is_immutable: member.is_immutable
+		}
 	}
 	s.structs[name] = ClassSymbolInfo{name: name, members_info: members_info}
 }
@@ -157,11 +161,13 @@ struct TypeExpr {
 struct ClassMember {
 	name string
 	type string
+	is_immutable bool
 }
 
 struct MemberAccess {
 	from Expr
 	member string
+	member_type string
 }
 
 struct ClassInstantiation {
@@ -349,10 +355,6 @@ fn (mut p Parser) parse_ident(ident string) Expr {
 		}
 	}
 
-	if p.inside_struct {
-		return p.parse_class_member(ident)
-	}
-
 	return match p.peek().type {
 		.increment, .decrement {UnaryExpr {ident: ident, op: p.next().text}}
 		.lparen {p.parse_call(ident)}
@@ -363,25 +365,34 @@ fn (mut p Parser) parse_ident(ident string) Expr {
 fn (mut p Parser) parse_member_access(from Expr) MemberAccess {
 	member_tok := p.next()
 	if member_tok.type != .identifier {parse_error("Expected identifier after member access")}
-	return MemberAccess {from: from, member: member_tok.text}
+	from_class := p.symbols.lookup_class(p.get_expr_type(from)) or {panic("Accessing member from non-class type")}
+	if !(member_tok.text in from_class.members_info) {panic("Accessing undefined member ${member_tok.text}")}
+	member_type := from_class.members_info[member_tok.text].type
+	return MemberAccess {from: from, member: member_tok.text, member_type: member_type}
 }
 
-fn (mut p Parser) parse_class_member(name string) ClassMember {
+fn (mut p Parser) parse_class_member() ClassMember {
+	mut is_immut := false
+	if p.peek().type == .kw_immutable {
+		is_immut = true
+		p.next()
+	}
+	member_name := p.peek().text
 	p.expect(.identifier)
 
 	type_tok := p.peek()
 	type_name := match type_tok.type {
 		.type {type_tok.text}
 		.identifier {
-				p.expect_ident_is_class(type_tok.text)
-				type_tok.text
-			}
-		else{parse_error("Expected type after class member ${name} in declaration, got ${p.peek().type}")}
+			p.expect_ident_is_class(type_tok.text)
+			type_tok.text
+		}
+		else{parse_error("Expected type after class member ${member_name} in declaration, got ${p.peek().type}")}
 	}
 
 	p.next()
 	p.expect(.semicolon)
-	return ClassMember{name: name, type: type_name}
+	return ClassMember{name: member_name, type: type_name is_immutable: is_immut}
 }
 
 fn (mut p Parser) parse_class_inst(name string) ClassInstantiation {
@@ -439,6 +450,20 @@ fn (mut p Parser) parse_print() PrintExpr {
 }
 
 fn (mut p Parser) parse_binary(left Expr, op string, prec Precedence) BinaryExpr {
+
+	if op in ['=', '+=', '-=', '*=', '/='] {
+		if left is MemberAccess {
+			from_type := p.get_expr_type(left.from)
+			if class_info := p.symbols.lookup_class(from_type) {
+			  if member_info := class_info.members_info[left.member] {
+				  if member_info.is_immutable {
+					  parse_error("Cannot assign to immutable member ${left.member} in class ${from_type}")
+				  }
+			  }
+			}
+		}
+	}
+
 	right := p.parse_expr(prec)
 	binary_expr := BinaryExpr{left, op, right}
 
@@ -513,13 +538,7 @@ fn (mut p Parser) get_expr_type(expr Expr) string {
 			fninfo.type
 		}
 		MemberAccess {
-			mut type_from := p.get_expr_type(expr.from)
-			classinfo := p.symbols.lookup_class(type_from)or{parse_error("Non-existant class ${type_from}")}
-			if expr.member in classinfo.members_info {
-				classinfo.members_info[expr.member].type
-			} else {
-				parse_error("Undefined class member ${expr.member}")
-			}
+			expr.member_type
 		}
 		ClassInstantiation {expr.name}
 		else {"Tried getting type of unexpected Expr"}
@@ -695,8 +714,8 @@ fn (mut p Parser) parse_class() ClassDecl {
 	p.expect(.identifier)
 	p.expect(.lbracket)
 	mut members := []ClassMember{}
-	for p.peek().type == .identifier {
-		members << p.parse_class_member(p.peek().text)
+	for p.peek().type != .rbracket {
+		members << p.parse_class_member()
 	}
 	p.expect(.rbracket)
 	p.symbols.define_class(name, members)
@@ -793,6 +812,10 @@ fn (mut p Parser) parse_block(no_scope bool) Block {
 }
 
 fn (mut p Parser) parse_program() ([]Stmt, SymbolTable) {
+	p.symbols.define_class('string',[
+		ClassMember{'len', 'int', true}
+	])
+
 	p.symbols.variable_scopes << map[string]VarSymbolInfo{}
 	for p.peek().type != .eof {
 		p.statements << p.parse_statement()