started work on c compiler

Cargo.lock

@@ -539,6 +539,10 @@ version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d71b6127be86fdcfddb610f7182ac57211d4b18a3e9c82eb2d17662f2227ad6a"
 
+[[package]]
+name = "c_compiler"
+version = "0.2.0"
+
 [[package]]
 name = "calloop"
 version = "0.13.0"

Cargo.toml

@@ -1,7 +1,7 @@
 cargo-features = ["codegen-backend"]
 
 [workspace]
-members = ["emulator", "common", "assembler", "dsa_editor", "compiler"]
+members = ["emulator", "common", "assembler", "dsa_editor", "compiler", "c_compiler"]
 resolver = "3"
 
 [workspace.package]

assembler/src/assembler/mod.rs

@@ -138,6 +138,11 @@ fn assemble(src: &Path) -> Result<Vec<Instruction>, AssembleError> {
     create_sections(&mut nodes)?;
     resolve_symbols(&mut nodes)?;
 
+    println!("Generating assembly output...");
+    for n in &nodes {
+        println!("{n}");
+    }
+
     let instructions = codegen(nodes)?;
     Ok(instructions)
 }

c_compiler/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "c_compiler"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+
+[dependencies]

c_compiler/code.c

@@ -0,0 +1,19 @@
+int factorial(int n) {
+  if (n <= 1) {
+    return 1;
+  }
+  return n * factorial(n - 1);
+}
+
+int add(int a, int b) { return a + b; }
+
+int main() {
+  int x;
+  x = 5;
+  int x = 5;
+  int result;
+  int result = 5;
+  result = x + factorial(5);
+  print(result);
+  return 0;
+}

c_compiler/compiler.py

@@ -0,0 +1,926 @@
+#!/usr/bin/env python3
+"""
+Simple C to DSA Assembly Compiler
+Supports a subset of C including:
+- int variables and functions
+- Arithmetic operations (+, -, *, /)
+- Comparisons (==, !=, <, >, <=, >=)
+- If/else statements
+- While loops
+- Function calls
+- Return statements
+"""
+
+import re
+import sys
+from typing import List, Dict, Optional, Tuple
+from dataclasses import dataclass
+from enum import Enum
+from pprint import pprint
+import json
+
+
+class TokenType(Enum):
+    # Keywords
+    INT = "int"
+    IF = "if"
+    ELSE = "else"
+    WHILE = "while"
+    RETURN = "return"
+
+    # Identifiers and literals
+    IDENTIFIER = "IDENTIFIER"
+    NUMBER = "NUMBER"
+
+    # Operators
+    PLUS = "+"
+    MINUS = "-"
+    STAR = "*"
+    SLASH = "/"
+    ASSIGN = "="
+    EQ = "=="
+    NE = "!="
+    LT = "<"
+    GT = ">"
+    LE = "<="
+    GE = ">="
+
+    # Delimiters
+    LPAREN = "("
+    RPAREN = ")"
+    LBRACE = "{"
+    RBRACE = "}"
+    SEMICOLON = ";"
+    COMMA = ","
+
+    EOF = "EOF"
+
+
+@dataclass
+class Token:
+    type: TokenType
+    value: str
+    line: int
+    col: int
+
+
+class Lexer:
+    def __init__(self, source: str):
+        self.source = source
+        self.pos = 0
+        self.line = 1
+        self.col = 1
+        self.tokens = []
+
+    def error(self, msg: str):
+        raise SyntaxError(f"Lexer error at line {self.line}, col {self.col}: {msg}")
+
+    def peek(self, offset: int = 0) -> Optional[str]:
+        pos = self.pos + offset
+        return self.source[pos] if pos < len(self.source) else None
+
+    def advance(self) -> Optional[str]:
+        if self.pos >= len(self.source):
+            return None
+        char = self.source[self.pos]
+        self.pos += 1
+        if char == "\n":
+            self.line += 1
+            self.col = 1
+        else:
+            self.col += 1
+        return char
+
+    def skip_whitespace(self):
+        while self.peek() and self.peek() in " \t\n\r":
+            self.advance()
+
+    def skip_comment(self):
+        if self.peek() == "/" and self.peek(1) == "/":
+            while self.peek() and self.peek() != "\n":
+                self.advance()
+            self.advance()  # skip newline
+
+    def read_number(self) -> str:
+        num = ""
+        while self.peek() and self.peek().isdigit():
+            num += self.advance()
+        return num
+
+    def read_identifier(self) -> str:
+        ident = ""
+        while self.peek() and (self.peek().isalnum() or self.peek() == "_"):
+            ident += self.advance()
+        return ident
+
+    def tokenize(self) -> List[Token]:
+        keywords = {
+            "int": TokenType.INT,
+            "if": TokenType.IF,
+            "else": TokenType.ELSE,
+            "while": TokenType.WHILE,
+            "return": TokenType.RETURN,
+        }
+
+        while self.pos < len(self.source):
+            self.skip_whitespace()
+            self.skip_comment()
+
+            if self.pos >= len(self.source):
+                break
+
+            line, col = self.line, self.col
+            char = self.peek()
+
+            # Numbers
+            if char.isdigit():
+                num = self.read_number()
+                self.tokens.append(Token(TokenType.NUMBER, num, line, col))
+
+            # Identifiers and keywords
+            elif char.isalpha() or char == "_":
+                ident = self.read_identifier()
+                token_type = keywords.get(ident, TokenType.IDENTIFIER)
+                self.tokens.append(Token(token_type, ident, line, col))
+
+            # Two-character operators
+            elif char == "=" and self.peek(1) == "=":
+                self.advance()
+                self.advance()
+                self.tokens.append(Token(TokenType.EQ, "==", line, col))
+            elif char == "!" and self.peek(1) == "=":
+                self.advance()
+                self.advance()
+                self.tokens.append(Token(TokenType.NE, "!=", line, col))
+            elif char == "<" and self.peek(1) == "=":
+                self.advance()
+                self.advance()
+                self.tokens.append(Token(TokenType.LE, "<=", line, col))
+            elif char == ">" and self.peek(1) == "=":
+                self.advance()
+                self.advance()
+                self.tokens.append(Token(TokenType.GE, ">=", line, col))
+
+            # Single-character operators
+            elif char == "+":
+                self.advance()
+                self.tokens.append(Token(TokenType.PLUS, "+", line, col))
+            elif char == "-":
+                self.advance()
+                self.tokens.append(Token(TokenType.MINUS, "-", line, col))
+            elif char == "*":
+                self.advance()
+                self.tokens.append(Token(TokenType.STAR, "*", line, col))
+            elif char == "/":
+                self.advance()
+                self.tokens.append(Token(TokenType.SLASH, "/", line, col))
+            elif char == "=":
+                self.advance()
+                self.tokens.append(Token(TokenType.ASSIGN, "=", line, col))
+            elif char == "<":
+                self.advance()
+                self.tokens.append(Token(TokenType.LT, "<", line, col))
+            elif char == ">":
+                self.advance()
+                self.tokens.append(Token(TokenType.GT, ">", line, col))
+            elif char == "(":
+                self.advance()
+                self.tokens.append(Token(TokenType.LPAREN, "(", line, col))
+            elif char == ")":
+                self.advance()
+                self.tokens.append(Token(TokenType.RPAREN, ")", line, col))
+            elif char == "{":
+                self.advance()
+                self.tokens.append(Token(TokenType.LBRACE, "{", line, col))
+            elif char == "}":
+                self.advance()
+                self.tokens.append(Token(TokenType.RBRACE, "}", line, col))
+            elif char == ";":
+                self.advance()
+                self.tokens.append(Token(TokenType.SEMICOLON, ";", line, col))
+            elif char == ",":
+                self.advance()
+                self.tokens.append(Token(TokenType.COMMA, ",", line, col))
+            else:
+                self.error(f"Unexpected character: {char}")
+
+        self.tokens.append(Token(TokenType.EOF, "", self.line, self.col))
+        return self.tokens
+
+
+# AST Node classes
+@dataclass
+class ASTNode:
+    pass
+
+
+@dataclass
+class Program(ASTNode):
+    declarations: List["Declaration"]
+
+
+@dataclass
+class Declaration(ASTNode):
+    pass
+
+
+@dataclass
+class FunctionDecl(Declaration):
+    name: str
+    params: List[str]
+    body: "CompoundStmt"
+
+
+@dataclass
+class VarDecl(Declaration):
+    name: str
+    init: Optional["Expression"] = None
+
+
+@dataclass
+class Statement(ASTNode):
+    pass
+
+
+@dataclass
+class CompoundStmt(Statement):
+    statements: List[Statement]
+
+
+@dataclass
+class ExprStmt(Statement):
+    expr: Optional["Expression"]
+
+
+@dataclass
+class IfStmt(Statement):
+    condition: "Expression"
+    then_stmt: Statement
+    else_stmt: Optional[Statement] = None
+
+
+@dataclass
+class WhileStmt(Statement):
+    condition: "Expression"
+    body: Statement
+
+
+@dataclass
+class ReturnStmt(Statement):
+    expr: Optional["Expression"]
+
+
+@dataclass
+class Expression(ASTNode):
+    pass
+
+
+@dataclass
+class BinaryOp(Expression):
+    op: str
+    left: Expression
+    right: Expression
+
+
+@dataclass
+class UnaryOp(Expression):
+    op: str
+    operand: Expression
+
+
+@dataclass
+class AssignExpr(Expression):
+    name: str
+    value: Expression
+
+
+@dataclass
+class VarExpr(Expression):
+    name: str
+
+
+@dataclass
+class NumberExpr(Expression):
+    value: int
+
+
+@dataclass
+class CallExpr(Expression):
+    name: str
+    args: List[Expression]
+
+
+class Parser:
+    def __init__(self, tokens: List[Token]):
+        self.tokens = tokens
+        self.pos = 0
+
+    def error(self, msg: str):
+        token = self.current()
+        raise SyntaxError(f"Parser error at line {token.line}, col {token.col}: {msg}")
+
+    def current(self) -> Token:
+        return self.tokens[self.pos] if self.pos < len(self.tokens) else self.tokens[-1]
+
+    def peek(self, offset: int = 0) -> Token:
+        pos = self.pos + offset
+        return self.tokens[pos] if pos < len(self.tokens) else self.tokens[-1]
+
+    def advance(self) -> Token:
+        token = self.current()
+        if self.pos < len(self.tokens) - 1:
+            self.pos += 1
+        return token
+
+    def expect(self, token_type: TokenType) -> Token:
+        token = self.current()
+        if token.type != token_type:
+            self.error(f"Expected {token_type.value}, got {token.type.value}")
+        return self.advance()
+
+    def parse(self) -> Program:
+        declarations = []
+        while self.current().type != TokenType.EOF:
+            declarations.append(self.parse_declaration())
+        return Program(declarations)
+
+    def parse_declaration(self) -> Declaration:
+        self.expect(TokenType.INT)
+        name = self.expect(TokenType.IDENTIFIER).value
+
+        if self.current().type == TokenType.LPAREN:
+            # Function declaration
+            self.advance()
+            params = []
+
+            if self.current().type != TokenType.RPAREN:
+                self.expect(TokenType.INT)
+                params.append(self.expect(TokenType.IDENTIFIER).value)
+
+                while self.current().type == TokenType.COMMA:
+                    self.advance()
+                    self.expect(TokenType.INT)
+                    params.append(self.expect(TokenType.IDENTIFIER).value)
+
+            self.expect(TokenType.RPAREN)
+            body = self.parse_compound_stmt()
+            return FunctionDecl(name, params, body)
+        else:
+            # Variable declaration
+            init = None
+            if self.current().type == TokenType.ASSIGN:
+                self.advance()
+                init = self.parse_expression()
+            self.expect(TokenType.SEMICOLON)
+            return VarDecl(name, init)
+
+    def parse_compound_stmt(self) -> CompoundStmt:
+        self.expect(TokenType.LBRACE)
+        statements = []
+
+        while self.current().type != TokenType.RBRACE:
+            statements.append(self.parse_statement())
+
+        self.expect(TokenType.RBRACE)
+        return CompoundStmt(statements)
+
+    def parse_statement(self) -> Statement:
+        token = self.current()
+
+        if token.type == TokenType.LBRACE:
+            return self.parse_compound_stmt()
+        elif token.type == TokenType.IF:
+            return self.parse_if_stmt()
+        elif token.type == TokenType.WHILE:
+            return self.parse_while_stmt()
+        elif token.type == TokenType.RETURN:
+            return self.parse_return_stmt()
+        elif token.type == TokenType.INT:
+            # Local variable declaration
+            self.advance()
+            name = self.expect(TokenType.IDENTIFIER).value
+            init = None
+            if self.current().type == TokenType.ASSIGN:
+                self.advance()
+                init = self.parse_expression()
+            self.expect(TokenType.SEMICOLON)
+            return ExprStmt(AssignExpr(name, init) if init else None)
+        else:
+            expr = (
+                self.parse_expression()
+                if self.current().type != TokenType.SEMICOLON
+                else None
+            )
+            self.expect(TokenType.SEMICOLON)
+            return ExprStmt(expr)
+
+    def parse_if_stmt(self) -> IfStmt:
+        self.expect(TokenType.IF)
+        self.expect(TokenType.LPAREN)
+        condition = self.parse_expression()
+        self.expect(TokenType.RPAREN)
+        then_stmt = self.parse_statement()
+
+        else_stmt = None
+        if self.current().type == TokenType.ELSE:
+            self.advance()
+            else_stmt = self.parse_statement()
+
+        return IfStmt(condition, then_stmt, else_stmt)
+
+    def parse_while_stmt(self) -> WhileStmt:
+        self.expect(TokenType.WHILE)
+        self.expect(TokenType.LPAREN)
+        condition = self.parse_expression()
+        self.expect(TokenType.RPAREN)
+        body = self.parse_statement()
+        return WhileStmt(condition, body)
+
+    def parse_return_stmt(self) -> ReturnStmt:
+        self.expect(TokenType.RETURN)
+        expr = None
+        if self.current().type != TokenType.SEMICOLON:
+            expr = self.parse_expression()
+        self.expect(TokenType.SEMICOLON)
+        return ReturnStmt(expr)
+
+    def parse_expression(self) -> Expression:
+        return self.parse_assignment()
+
+    def parse_assignment(self) -> Expression:
+        expr = self.parse_comparison()
+
+        if self.current().type == TokenType.ASSIGN:
+            if not isinstance(expr, VarExpr):
+                self.error("Invalid assignment target")
+            self.advance()
+            value = self.parse_assignment()
+            return AssignExpr(expr.name, value)
+
+        return expr
+
+    def parse_comparison(self) -> Expression:
+        expr = self.parse_additive()
+
+        while self.current().type in [
+            TokenType.EQ,
+            TokenType.NE,
+            TokenType.LT,
+            TokenType.GT,
+            TokenType.LE,
+            TokenType.GE,
+        ]:
+            op = self.advance().value
+            right = self.parse_additive()
+            expr = BinaryOp(op, expr, right)
+
+        return expr
+
+    def parse_additive(self) -> Expression:
+        expr = self.parse_multiplicative()
+
+        while self.current().type in [TokenType.PLUS, TokenType.MINUS]:
+            op = self.advance().value
+            right = self.parse_multiplicative()
+            expr = BinaryOp(op, expr, right)
+
+        return expr
+
+    def parse_multiplicative(self) -> Expression:
+        expr = self.parse_unary()
+
+        while self.current().type in [TokenType.STAR, TokenType.SLASH]:
+            op = self.advance().value
+            right = self.parse_unary()
+            expr = BinaryOp(op, expr, right)
+
+        return expr
+
+    def parse_unary(self) -> Expression:
+        if self.current().type in [TokenType.PLUS, TokenType.MINUS]:
+            op = self.advance().value
+            operand = self.parse_unary()
+            return UnaryOp(op, operand)
+
+        return self.parse_primary()
+
+    def parse_primary(self) -> Expression:
+        token = self.current()
+
+        if token.type == TokenType.NUMBER:
+            self.advance()
+            return NumberExpr(int(token.value))
+
+        elif token.type == TokenType.IDENTIFIER:
+            name = self.advance().value
+
+            if self.current().type == TokenType.LPAREN:
+                # Function call
+                self.advance()
+                args = []
+
+                if self.current().type != TokenType.RPAREN:
+                    args.append(self.parse_expression())
+                    while self.current().type == TokenType.COMMA:
+                        self.advance()
+                        args.append(self.parse_expression())
+
+                self.expect(TokenType.RPAREN)
+                return CallExpr(name, args)
+            else:
+                return VarExpr(name)
+
+        elif token.type == TokenType.LPAREN:
+            self.advance()
+            expr = self.parse_expression()
+            self.expect(TokenType.RPAREN)
+            return expr
+
+        else:
+            self.error(f"Unexpected token: {token.type.value}")
+
+
+class CodeGenerator:
+    def __init__(self):
+        self.output = []
+        self.label_counter = 0
+        self.string_counter = 0
+        self.functions = {}
+        self.current_function = None
+        self.local_vars = {}
+        self.global_vars = {}
+        self.register_pool = [f"rg{i:x}" for i in range(16)]
+        self.used_registers = set()
+
+    def new_label(self, prefix: str = "L") -> str:
+        label = f"{prefix}{self.label_counter}"
+        self.label_counter += 1
+        return label
+
+    def allocate_register(self) -> str:
+        for reg in self.register_pool:
+            if reg not in self.used_registers:
+                self.used_registers.add(reg)
+                return reg
+        raise RuntimeError("Out of registers")
+
+    def free_register(self, reg: str):
+        self.used_registers.discard(reg)
+
+    def emit(self, code: str):
+        self.output.append(code)
+
+    def generate(self, program: Program) -> str:
+        # Emit data section
+        self.emit("// Global variables")
+        for decl in program.declarations:
+            if isinstance(decl, VarDecl):
+                self.global_vars[decl.name] = f"var_{decl.name}"
+                if decl.init:
+                    if isinstance(decl.init, NumberExpr):
+                        self.emit(f"dw var_{decl.name}: {decl.init.value}")
+                    else:
+                        self.emit(f"dw var_{decl.name}: 0")
+                else:
+                    self.emit(f"dw var_{decl.name}: 0")
+
+        self.emit("")
+        self.emit("// Entry point")
+        self.emit("dw stack_bottom: 0x10000")
+        self.emit("")
+        self.emit("init:")
+        self.emit("    ldw stack_bottom, spr")
+        self.emit("    mov spr, bpr")
+
+        self.emit("    push zero")
+        self.emit("    call main")
+        self.emit("    pop rg0")
+        self.emit("    hlt")
+        self.emit("")
+
+        # Emit functions
+        for decl in program.declarations:
+            if isinstance(decl, FunctionDecl):
+                self.generate_function(decl)
+
+        return "\n".join(self.output)
+
+    def generate_function(self, func: FunctionDecl):
+        self.current_function = func.name
+        self.functions[func.name] = func
+        self.local_vars = {}
+
+        # Map parameters to stack offsets
+        # Parameters start at bpr+8 (after return addr at bpr+4)
+        for i, param in enumerate(func.params):
+            self.local_vars[param] = 8 + (i * 4)
+
+        self.emit(f"{func.name}:")
+        self.emit("    push bpr")
+        self.emit("    mov spr, bpr")
+        self.emit("")
+
+        # Generate function body
+        self.generate_compound_stmt(func.body)
+
+        # Default return if no explicit return
+        self.emit("// default return")
+        self.emit(f"{func.name}_end:")
+        self.emit("    mov bpr, spr")
+        self.emit("    pop bpr")
+        self.emit("    return")
+        self.emit("")
+
+    def generate_compound_stmt(self, stmt: CompoundStmt):
+        for s in stmt.statements:
+            self.generate_statement(s)
+
+    def generate_statement(self, stmt: Statement):
+        if isinstance(stmt, CompoundStmt):
+            self.generate_compound_stmt(stmt)
+        elif isinstance(stmt, ExprStmt):
+            if stmt.expr:
+                reg = self.generate_expression(stmt.expr)
+                self.free_register(reg)
+        elif isinstance(stmt, IfStmt):
+            self.generate_if_stmt(stmt)
+        elif isinstance(stmt, WhileStmt):
+            self.generate_while_stmt(stmt)
+        elif isinstance(stmt, ReturnStmt):
+            self.generate_return_stmt(stmt)
+
+    def generate_if_stmt(self, stmt: IfStmt):
+        else_label = self.new_label("else")
+        end_label = self.new_label("endif")
+
+        # Evaluate condition
+        cond_reg = self.generate_expression(stmt.condition)
+        self.emit(f"    cmp {cond_reg}, zero")
+        self.free_register(cond_reg)
+
+        if stmt.else_stmt:
+            self.emit(f"    jeq {else_label}")
+        else:
+            self.emit(f"    jeq {end_label}")
+
+        # Then branch
+        self.generate_statement(stmt.then_stmt)
+
+        if stmt.else_stmt:
+            self.emit(f"    jmp {end_label}")
+            self.emit(f"{else_label}:")
+            self.generate_statement(stmt.else_stmt)
+
+        self.emit(f"{end_label}:")
+
+    def generate_while_stmt(self, stmt: WhileStmt):
+        start_label = self.new_label("while_start")
+        end_label = self.new_label("while_end")
+
+        self.emit(f"{start_label}:")
+
+        # Evaluate condition
+        cond_reg = self.generate_expression(stmt.condition)
+        self.emit(f"    cmp {cond_reg}, zero")
+        self.free_register(cond_reg)
+        self.emit(f"    jeq {end_label}")
+
+        # Loop body
+        self.generate_statement(stmt.body)
+        self.emit(f"    jmp {start_label}")
+
+        self.emit(f"{end_label}:")
+
+    def generate_return_stmt(self, stmt: ReturnStmt):
+        if stmt.expr:
+            reg = self.generate_expression(stmt.expr)
+            # Store return value at spr+8 according to calling convention
+            self.emit(f"    stw {reg}, spr, 8")
+            self.free_register(reg)
+        self.emit(f"    jmp {self.current_function}_end")
+
+    def generate_expression(self, expr: Expression) -> str:
+        if isinstance(expr, NumberExpr):
+            reg = self.allocate_register()
+            if expr.value <= 0xFFFF and expr.value >= 0:
+                self.emit(f"    lli {expr.value}, {reg}")
+                if expr.value > 0xFF:
+                    self.emit(f"    lui {expr.value >> 16}, {reg}")
+            else:
+                self.emit(f"    lli {expr.value & 0xFFFF}, {reg}")
+                self.emit(f"    lui {(expr.value >> 16) & 0xFFFF}, {reg}")
+            return reg
+
+        elif isinstance(expr, VarExpr):
+            reg = self.allocate_register()
+            if expr.name in self.local_vars:
+                offset = self.local_vars[expr.name]
+                self.emit(f"    ldw bpr, {reg}, {offset}")
+            elif expr.name in self.global_vars:
+                label = self.global_vars[expr.name]
+                self.emit(f"    ldw {label}, {reg}")
+            else:
+                raise RuntimeError(f"Undefined variable: {expr.name}")
+            return reg
+
+        elif isinstance(expr, AssignExpr):
+            value_reg = self.generate_expression(expr.value)
+
+            if expr.name in self.local_vars:
+                offset = self.local_vars[expr.name]
+                self.emit(f"    stw {value_reg}, bpr, {offset}")
+            elif expr.name in self.global_vars:
+                label = self.global_vars[expr.name]
+                self.emit(f"    stw {value_reg}, {label}")
+            else:
+                # New local variable - allocate after params and return value space
+                # Start local variables at offset -4 from bpr (growing downward)
+                offset = -(len([v for v in self.local_vars.values() if v < 0]) + 1) * 4
+                self.local_vars[expr.name] = offset
+                self.emit(f"    stw {value_reg}, bpr, {offset}")
+
+            return value_reg
+
+        elif isinstance(expr, BinaryOp):
+            return self.generate_binary_op(expr)
+
+        elif isinstance(expr, UnaryOp):
+            operand_reg = self.generate_expression(expr.operand)
+            result_reg = self.allocate_register()
+
+            if expr.op == "-":
+                self.emit(f"    lwi 0, {result_reg}")
+                self.emit(f"    sub {result_reg}, {operand_reg}, {result_reg}")
+            else:  # +
+                self.emit(f"    mov {operand_reg}, {result_reg}")
+
+            self.free_register(operand_reg)
+            return result_reg
+
+        elif isinstance(expr, CallExpr):
+            # First, make space for return value (must be pushed BEFORE arguments)
+            temp_reg = self.allocate_register()
+
+            # Then push arguments in reverse order
+            arg_regs = []
+            for arg in reversed(expr.args):
+                reg = self.generate_expression(arg)
+                self.emit(f"    push {reg}")
+                arg_regs.append(reg)
+
+            # Call function
+            self.emit(f"    call {expr.name}")
+
+            # Get return value (it's now on top of stack)
+            self.emit(f"    pop {temp_reg}")
+
+            # Clean up remaining args
+            for i in range(len(arg_regs) - 1):
+                self.emit(f"    pop zero")
+
+            # Free the arg registers
+            for reg in arg_regs:
+                self.free_register(reg)
+
+            return temp_reg
+
+        else:
+            raise RuntimeError(f"Unknown expression type: {type(expr)}")
+
+    def generate_binary_op(self, expr: BinaryOp) -> str:
+        # For operations that might contain function calls, we need to be careful
+        # about register allocation. Evaluate left, save it, evaluate right.
+        left_reg = self.generate_expression(expr.left)
+
+        # If right side contains a function call, we need to save left_reg
+        # For now, always save to be safe
+        saved_reg = self.allocate_register()
+        self.emit(f"    mov {left_reg}, {saved_reg}")
+        self.free_register(left_reg)
+
+        right_reg = self.generate_expression(expr.right)
+        result_reg = self.allocate_register()
+
+        if expr.op == "+":
+            self.emit(f"    add {left_reg}, {right_reg}, {result_reg}")
+        elif expr.op == "-":
+            self.emit(f"    sub {left_reg}, {right_reg}, {result_reg}")
+        elif expr.op == "*":
+            # Simple multiplication using loop
+            temp_label = self.new_label("mult")
+            end_label = self.new_label("mult_end")
+            self.emit(f"    lli 0, {result_reg}")
+            self.emit(f"{temp_label}:")
+            self.emit(f"    cmp {right_reg}, zero")
+            self.emit(f"    jeq {end_label}")
+            self.emit(f"    add {result_reg}, {left_reg}, {result_reg}")
+            self.emit(f"    dec {right_reg}")
+            self.emit(f"    jmp {temp_label}")
+            self.emit(f"{end_label}:")
+        elif expr.op == "/":
+            # Simple division using loop
+            temp_label = self.new_label("div")
+            end_label = self.new_label("div_end")
+            self.emit(f"    lli 0, {result_reg}")
+            self.emit(f"{temp_label}:")
+            self.emit(f"    cmp {left_reg}, {right_reg}")
+            self.emit(f"    jlt {end_label}")
+            self.emit(f"    sub {left_reg}, {right_reg}, {left_reg}")
+            self.emit(f"    inc {result_reg}")
+            self.emit(f"    jmp {temp_label}")
+            self.emit(f"{end_label}:")
+        elif expr.op in ["==", "!=", "<", ">", "<=", ">="]:
+            self.emit(f"    cmp {left_reg}, {right_reg}")
+
+            # Result is 1 if condition true, 0 otherwise
+            self.emit(f"    lli 0, {result_reg}")
+            true_label = self.new_label("cmp_true")
+            end_label = self.new_label("cmp_end")
+
+            if expr.op == "==":
+                self.emit(f"    jeq {true_label}")
+            elif expr.op == "!=":
+                self.emit(f"    jne {true_label}")
+            elif expr.op == "<":
+                self.emit(f"    jlt {true_label}")
+            elif expr.op == ">":
+                self.emit(f"    jgt {true_label}")
+            elif expr.op == "<=":
+                self.emit(f"    jle {true_label}")
+            elif expr.op == ">=":
+                self.emit(f"    jge {true_label}")
+
+            self.emit(f"    jmp {end_label}")
+            self.emit(f"{true_label}:")
+            self.emit(f"    lli 1, {result_reg}")
+            self.emit(f"{end_label}:")
+
+        self.free_register(left_reg)
+        self.free_register(right_reg)
+        return result_reg
+
+
+def compile_c_to_asm(source: str) -> str:
+    """Compile C source code to DSA assembly."""
+    lexer = Lexer(source)
+    tokens = lexer.tokenize()
+
+    parser = Parser(tokens)
+    ast = parser.parse()
+
+    codegen = CodeGenerator()
+    assembly = codegen.generate(ast)
+
+    return assembly
+
+
+def main():
+    if len(sys.argv) < 2:
+        print("Usage: python compiler.py <input.c> [output.dsa]")
+        sys.exit(1)
+
+    input_file = sys.argv[1]
+    output_file = sys.argv[2] if len(sys.argv) > 2 else input_file.replace(".c", ".dsa")
+
+    with open(input_file, "r") as f:
+        source = f.read()
+
+    try:
+        assembly = compile_c_to_asm(source)
+
+        with open(output_file, "w") as f:
+            f.write(assembly)
+
+        print(f"Successfully compiled {input_file} to {output_file}")
+    except (SyntaxError, RuntimeError) as e:
+        print(f"Compilation error: {e}")
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()
+    # # Example usage
+    # if len(sys.argv) > 1:
+    #     example_c = sys.argv[1]
+
+    # else:
+    #     example_c = """
+    # int factorial(int n) {
+    #     if (n <= 1) {
+    #         return 1;
+    #     }
+    #     return n * factorial(n - 1);
+    # }
+
+    # int main() {
+    #     int result;
+    #     result = factorial(5);
+    #     return result;
+    # }
+    #     """
+
+    # print("Example C program:")
+    # print(example_c)
+    # print("\n" + "="*60 + "\n")
+    # print("Generated DSA assembly:")
+    # print(compile_c_to_asm(example_c))

c_compiler/src/codegen.rs

@@ -0,0 +1,13 @@
+use crate::parser::Program;
+
+pub struct CodeGenerator;
+
+impl CodeGenerator {
+    pub fn new(ast: Program) -> Self {
+        CodeGenerator {}
+    }
+
+    pub fn run(&mut self) -> Result<String, String> {
+        Ok(String::new())
+    }
+}

c_compiler/src/lexer.rs

@@ -0,0 +1,265 @@
+// ============================================================================
+// Token Types
+// ============================================================================
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum TokenType {
+    // Keywords
+    Int,
+    If,
+    Else,
+    While,
+    Return,
+
+    // Identifiers and literals
+    Identifier(String),
+    Number(i32),
+
+    // Operators
+    Plus,
+    Minus,
+    Star,
+    Slash,
+    Assign,
+    Eq,
+    Ne,
+    Lt,
+    Gt,
+    Le,
+    Ge,
+
+    // Delimiters
+    LParen,
+    RParen,
+    LBrace,
+    RBrace,
+    Semicolon,
+    Comma,
+
+    Eof,
+}
+
+#[derive(Debug, Clone)]
+pub struct Token {
+    pub token_type: TokenType,
+    pub line: usize,
+    pub col: usize,
+}
+
+impl Token {
+    pub fn new(token_type: TokenType, line: usize, col: usize) -> Self {
+        Self {
+            token_type,
+            line,
+            col,
+        }
+    }
+}
+
+// ============================================================================
+// Lexer
+// ============================================================================
+
+pub struct Lexer {
+    source: Vec<char>,
+    pos: usize,
+    line: usize,
+    col: usize,
+}
+
+impl Lexer {
+    pub fn new(source: &str) -> Self {
+        Self {
+            source: source.chars().collect(),
+            pos: 0,
+            line: 1,
+            col: 1,
+        }
+    }
+
+    fn error(&self, msg: &str) -> String {
+        format!(
+            "Lexer error at line {}, col {}: {}",
+            self.line, self.col, msg
+        )
+    }
+
+    fn peek(&self, offset: usize) -> Option<char> {
+        self.source.get(self.pos + offset).copied()
+    }
+
+    fn advance(&mut self) -> Option<char> {
+        if self.pos >= self.source.len() {
+            return None;
+        }
+        let ch = self.source[self.pos];
+        self.pos += 1;
+        if ch == '\n' {
+            self.line += 1;
+            self.col = 1;
+        } else {
+            self.col += 1;
+        }
+        Some(ch)
+    }
+
+    fn skip_whitespace(&mut self) {
+        while let Some(ch) = self.peek(0) {
+            if ch.is_whitespace() {
+                self.advance();
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn skip_comment(&mut self) {
+        if self.peek(0) == Some('/') && self.peek(1) == Some('/') {
+            while let Some(ch) = self.peek(0) {
+                if ch == '\n' {
+                    break;
+                }
+                self.advance();
+            }
+        }
+    }
+
+    fn read_number(&mut self) -> i32 {
+        let mut num_str = String::new();
+        while let Some(ch) = self.peek(0) {
+            if ch.is_ascii_digit() {
+                num_str.push(ch);
+                self.advance();
+            } else {
+                break;
+            }
+        }
+        num_str.parse().unwrap_or(0)
+    }
+
+    fn read_identifier(&mut self) -> String {
+        let mut ident = String::new();
+        while let Some(ch) = self.peek(0) {
+            if ch.is_alphanumeric() || ch == '_' {
+                ident.push(ch);
+                self.advance();
+            } else {
+                break;
+            }
+        }
+        ident
+    }
+
+    pub fn tokenize(&mut self) -> Result<Vec<Token>, String> {
+        let mut tokens = Vec::new();
+
+        loop {
+            self.skip_whitespace();
+            self.skip_comment();
+
+            if self.pos >= self.source.len() {
+                break;
+            }
+
+            let line = self.line;
+            let col = self.col;
+            let ch = self.peek(0).unwrap();
+
+            let token_type = if ch.is_ascii_digit() {
+                let num = self.read_number();
+                TokenType::Number(num)
+            } else if ch.is_alphabetic() || ch == '_' {
+                let ident = self.read_identifier();
+                match ident.as_str() {
+                    "int" => TokenType::Int,
+                    "if" => TokenType::If,
+                    "else" => TokenType::Else,
+                    "while" => TokenType::While,
+                    "return" => TokenType::Return,
+                    _ => TokenType::Identifier(ident),
+                }
+            } else {
+                match ch {
+                    '=' if self.peek(1) == Some('=') => {
+                        self.advance();
+                        self.advance();
+                        TokenType::Eq
+                    }
+                    '!' if self.peek(1) == Some('=') => {
+                        self.advance();
+                        self.advance();
+                        TokenType::Ne
+                    }
+                    '<' if self.peek(1) == Some('=') => {
+                        self.advance();
+                        self.advance();
+                        TokenType::Le
+                    }
+                    '>' if self.peek(1) == Some('=') => {
+                        self.advance();
+                        self.advance();
+                        TokenType::Ge
+                    }
+                    '+' => {
+                        self.advance();
+                        TokenType::Plus
+                    }
+                    '-' => {
+                        self.advance();
+                        TokenType::Minus
+                    }
+                    '*' => {
+                        self.advance();
+                        TokenType::Star
+                    }
+                    '/' => {
+                        self.advance();
+                        TokenType::Slash
+                    }
+                    '=' => {
+                        self.advance();
+                        TokenType::Assign
+                    }
+                    '<' => {
+                        self.advance();
+                        TokenType::Lt
+                    }
+                    '>' => {
+                        self.advance();
+                        TokenType::Gt
+                    }
+                    '(' => {
+                        self.advance();
+                        TokenType::LParen
+                    }
+                    ')' => {
+                        self.advance();
+                        TokenType::RParen
+                    }
+                    '{' => {
+                        self.advance();
+                        TokenType::LBrace
+                    }
+                    '}' => {
+                        self.advance();
+                        TokenType::RBrace
+                    }
+                    ';' => {
+                        self.advance();
+                        TokenType::Semicolon
+                    }
+                    ',' => {
+                        self.advance();
+                        TokenType::Comma
+                    }
+                    _ => return Err(self.error(&format!("Unexpected character: {}", ch))),
+                }
+            };
+
+            tokens.push(Token::new(token_type, line, col));
+        }
+
+        tokens.push(Token::new(TokenType::Eof, self.line, self.col));
+        Ok(tokens)
+    }
+}

c_compiler/src/main.rs

@@ -0,0 +1,72 @@
+use std::fmt;
+
+use crate::{codegen::CodeGenerator, lexer::Lexer, parser::Parser};
+
+pub mod codegen;
+pub mod lexer;
+pub mod parser;
+
+// ============================================================================
+// Main & Tests
+// ============================================================================
+
+fn main() {
+    // read from input file: syntax "c_compiler <src.c> [output.dsa]"
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() < 2 {
+        eprintln!("Usage: c_compiler <src.c> [output.dsa]");
+        return;
+    }
+
+    let input_file = &args[1];
+    let output_file = if args.len() > 2 {
+        &args[2]
+    } else {
+        "output.dsa"
+    };
+
+    // read input
+    let input = std::fs::read_to_string(input_file).expect("Failed to read input file");
+
+    // Lexing
+    let mut lexer = Lexer::new(&input);
+    let tokens = match lexer.tokenize() {
+        Ok(tokens) => tokens,
+        Err(e) => {
+            eprintln!("Lexing error: {}", e);
+            return;
+        }
+    };
+
+    println!("Tokens:");
+    for token in &tokens {
+        println!("  {:?}", token.token_type);
+    }
+    println!();
+
+    // Parsing
+    let mut parser = Parser::new(tokens);
+    let ast = match parser.parse() {
+        Ok(ast) => ast,
+        Err(e) => {
+            eprintln!("Parsing error: {}", e);
+            return;
+        }
+    };
+
+    println!("AST:");
+    println!("{:#?}", ast);
+
+    // Code Gen
+    let mut generator = CodeGenerator::new(ast);
+    let result = match generator.run() {
+        Ok(code) => code,
+        Err(e) => {
+            eprintln!("Parsing error: {}", e);
+            return;
+        }
+    };
+
+    println!("CODE:");
+    println!("{:#?}", result);
+}

c_compiler/src/parser.rs

@@ -0,0 +1,558 @@
+// ============================================================================
+// AST Node Types
+// ============================================================================
+
+use std::fmt;
+
+use crate::lexer::{Token, TokenType};
+
+#[derive(Debug, Clone)]
+pub struct Program {
+    pub declarations: Vec<Declaration>,
+}
+
+#[derive(Debug, Clone)]
+pub enum Declaration {
+    Function {
+        name: String,
+        return_type: Type,
+        params: Vec<Parameter>,
+        body: Statement,
+    },
+    Variable {
+        name: String,
+        init: Option<Expression>,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub struct Parameter {
+    pub name: String,
+    pub param_type: Type,
+}
+
+#[derive(Debug, Clone)]
+pub enum Type {
+    Int,
+    Long,
+    Float,
+    Double,
+    Char,
+    Void,
+    Ptr(Box<Type>),
+    Array(Box<Type>, usize),
+    Struct(String),
+}
+
+#[derive(Debug, Clone)]
+pub enum Statement {
+    Compound {
+        statements: Vec<Statement>,
+    },
+    Assign {
+        // left side
+        name: String,
+        declare_type: Option<Type>,
+
+        // right side
+        value: Option<Box<Expression>>,
+    },
+    Expression {
+        expr: Expression,
+    },
+    If {
+        condition: Expression,
+        then_stmt: Box<Statement>,
+        else_stmt: Option<Box<Statement>>,
+    },
+    While {
+        condition: Expression,
+        body: Box<Statement>,
+    },
+    Return {
+        expr: Option<Expression>,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub enum Expression {
+    Empty,
+    Binary {
+        op: BinaryOperator,
+        left: Box<Expression>,
+        right: Box<Expression>,
+    },
+    Unary {
+        op: UnaryOperator,
+        operand: Box<Expression>,
+    },
+    Variable {
+        name: String,
+        expr_type: Option<Type>,
+    },
+    Number {
+        value: i32,
+    },
+    Call {
+        name: String,
+        args: Vec<Expression>,
+    },
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum BinaryOperator {
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Eq,
+    Ne,
+    Lt,
+    Gt,
+    Le,
+    Ge,
+}
+
+impl fmt::Display for BinaryOperator {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            BinaryOperator::Add => write!(f, "+"),
+            BinaryOperator::Sub => write!(f, "-"),
+            BinaryOperator::Mul => write!(f, "*"),
+            BinaryOperator::Div => write!(f, "/"),
+            BinaryOperator::Eq => write!(f, "=="),
+            BinaryOperator::Ne => write!(f, "!="),
+            BinaryOperator::Lt => write!(f, "<"),
+            BinaryOperator::Gt => write!(f, ">"),
+            BinaryOperator::Le => write!(f, "<="),
+            BinaryOperator::Ge => write!(f, ">="),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum UnaryOperator {
+    Plus,
+    Minus,
+}
+
+impl fmt::Display for UnaryOperator {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            UnaryOperator::Plus => write!(f, "+"),
+            UnaryOperator::Minus => write!(f, "-"),
+        }
+    }
+}
+
+// ============================================================================
+// Parser
+// ============================================================================
+
+pub struct Parser {
+    tokens: Vec<Token>,
+    pos: usize,
+}
+
+impl Parser {
+    pub fn new(tokens: Vec<Token>) -> Self {
+        Self { tokens, pos: 0 }
+    }
+
+    fn error(&self, msg: &str) -> String {
+        let token = self.current();
+        format!(
+            "Parser error at line {}, col {}: {}",
+            token.line, token.col, msg
+        )
+    }
+
+    fn current(&self) -> &Token {
+        self.tokens
+            .get(self.pos)
+            .unwrap_or_else(|| self.tokens.last().unwrap())
+    }
+
+    fn peek(&self, offset: usize) -> &Token {
+        self.tokens
+            .get(self.pos + offset)
+            .unwrap_or_else(|| self.tokens.last().unwrap())
+    }
+
+    fn advance(&mut self) -> &Token {
+        if self.pos < self.tokens.len() - 1 {
+            self.pos += 1;
+        }
+        self.current()
+    }
+
+    fn expect(&mut self, expected: TokenType) -> Result<Token, String> {
+        let token = self.current().clone();
+        if std::mem::discriminant(&token.token_type) != std::mem::discriminant(&expected)
+        {
+            return Err(self.error(&format!(
+                "Expected {:?}, got {:?}",
+                expected, token.token_type
+            )));
+        }
+        self.advance();
+        Ok(token)
+    }
+
+    pub fn parse(&mut self) -> Result<Program, String> {
+        let mut declarations = Vec::new();
+
+        while !matches!(self.current().token_type, TokenType::Eof) {
+            declarations.push(self.parse_declaration()?);
+        }
+
+        Ok(Program { declarations })
+    }
+
+    fn parse_declaration(&mut self) -> Result<Declaration, String> {
+        self.expect(TokenType::Int)?;
+
+        let name = match &self.current().token_type {
+            TokenType::Identifier(s) => s.clone(),
+            _ => return Err(self.error("Expected identifier")),
+        };
+        self.advance();
+
+        match &self.current().token_type {
+            TokenType::LParen => {
+                // Function declaration
+                self.advance();
+                let mut params = Vec::<Parameter>::new();
+
+                if !matches!(self.current().token_type, TokenType::RParen) {
+                    self.expect(TokenType::Int)?;
+
+                    match &self.current().token_type {
+                        TokenType::Identifier(s) => {
+                            params.push(Parameter {
+                                name: s.clone(),
+                                param_type: Type::Int,
+                            });
+                            self.advance();
+                        }
+                        _ => return Err(self.error("Expected parameter name")),
+                    }
+
+                    while matches!(self.current().token_type, TokenType::Comma) {
+                        self.advance();
+                        self.expect(TokenType::Int)?;
+
+                        match &self.current().token_type {
+                            TokenType::Identifier(s) => {
+                                params.push(Parameter {
+                                    name: s.clone(),
+                                    param_type: Type::Int,
+                                });
+                                self.advance();
+                            }
+                            _ => return Err(self.error("Expected parameter name")),
+                        }
+                    }
+                }
+
+                self.expect(TokenType::RParen)?;
+                let body = self.parse_compound_stmt()?;
+
+                Ok(Declaration::Function {
+                    name,
+                    params,
+                    body,
+                    return_type: Type::Int,
+                })
+            }
+            _ => {
+                // Variable declaration
+                let init = if matches!(self.current().token_type, TokenType::Assign) {
+                    self.advance();
+                    Some(self.parse_expression()?)
+                } else {
+                    None
+                };
+
+                self.expect(TokenType::Semicolon)?;
+                Ok(Declaration::Variable { name, init })
+            }
+        }
+    }
+
+    fn parse_compound_stmt(&mut self) -> Result<Statement, String> {
+        self.expect(TokenType::LBrace)?;
+        let mut statements = Vec::new();
+
+        while !matches!(self.current().token_type, TokenType::RBrace) {
+            statements.push(self.parse_statement()?);
+        }
+
+        self.expect(TokenType::RBrace)?;
+        Ok(Statement::Compound { statements })
+    }
+
+    fn parse_statement(&mut self) -> Result<Statement, String> {
+        match &self.current().token_type {
+            TokenType::LBrace => Ok(self.parse_compound_stmt()?),
+            TokenType::If => self.parse_if_stmt(),
+            TokenType::While => self.parse_while_stmt(),
+            TokenType::Return => self.parse_return_stmt(),
+            TokenType::Identifier(name) => {
+                let name = name.clone();
+
+                // peek ahead for open paren (func call expr)
+                if matches!(self.peek(1).token_type, TokenType::LParen) {
+                    let expr = self.parse_expression()?; // a function call expr
+                    self.expect(TokenType::Semicolon)?;
+                    return Ok(Statement::Expression { expr });
+                }
+
+                self.advance(); // advance past identifier
+
+                // assignment expression
+                if matches!(self.current().token_type, TokenType::Assign) {
+                    self.advance();
+                    let expr = self.parse_expression()?;
+
+                    self.expect(TokenType::Semicolon)?;
+                    Ok(Statement::Assign {
+                        name,
+                        value: Some(Box::new(expr)),
+                        declare_type: None,
+                    })
+                }
+                // var expression
+                else {
+                    self.expect(TokenType::Semicolon)?;
+                    Ok(Statement::Expression {
+                        expr: Expression::Variable {
+                            name,
+                            expr_type: None,
+                        },
+                    })
+                }
+            }
+            TokenType::Int => {
+                // Local variable declaration
+                self.advance();
+                let name = match &self.current().token_type {
+                    TokenType::Identifier(s) => s.clone(),
+                    _ => return Err(self.error("Expected variable name")),
+                };
+                self.advance();
+
+                let init = if matches!(self.current().token_type, TokenType::Assign) {
+                    self.advance();
+                    Some(self.parse_expression()?)
+                } else {
+                    None
+                };
+
+                self.expect(TokenType::Semicolon)?;
+
+                // Convert to assignment expression statement
+                let expr = if let Some(init_expr) = init {
+                    Statement::Assign {
+                        name,
+                        value: Some(Box::new(init_expr)),
+                        declare_type: Some(Type::Int),
+                    }
+                } else {
+                    Statement::Assign {
+                        name,
+                        value: None,
+                        declare_type: Some(Type::Int),
+                    }
+                };
+
+                Ok(expr)
+            }
+            _ => {
+                let expr = if matches!(self.current().token_type, TokenType::Semicolon) {
+                    Expression::Empty
+                } else {
+                    self.parse_expression()?
+                };
+
+                self.expect(TokenType::Semicolon)?;
+                Ok(Statement::Expression { expr })
+            }
+        }
+    }
+
+    fn parse_if_stmt(&mut self) -> Result<Statement, String> {
+        self.expect(TokenType::If)?;
+        self.expect(TokenType::LParen)?;
+        let condition = self.parse_expression()?;
+        self.expect(TokenType::RParen)?;
+        let then_stmt = Box::new(self.parse_statement()?);
+
+        let else_stmt = if matches!(self.current().token_type, TokenType::Else) {
+            self.advance();
+            Some(Box::new(self.parse_statement()?))
+        } else {
+            None
+        };
+
+        Ok(Statement::If {
+            condition,
+            then_stmt,
+            else_stmt,
+        })
+    }
+
+    fn parse_while_stmt(&mut self) -> Result<Statement, String> {
+        self.expect(TokenType::While)?;
+        self.expect(TokenType::LParen)?;
+        let condition = self.parse_expression()?;
+        self.expect(TokenType::RParen)?;
+        let body = Box::new(self.parse_statement()?);
+
+        Ok(Statement::While { condition, body })
+    }
+
+    fn parse_return_stmt(&mut self) -> Result<Statement, String> {
+        self.expect(TokenType::Return)?;
+
+        let expr = if matches!(self.current().token_type, TokenType::Semicolon) {
+            None
+        } else {
+            Some(self.parse_expression()?)
+        };
+
+        self.expect(TokenType::Semicolon)?;
+        Ok(Statement::Return { expr })
+    }
+
+    fn parse_expression(&mut self) -> Result<Expression, String> {
+        self.parse_comparison()
+    }
+
+    fn parse_comparison(&mut self) -> Result<Expression, String> {
+        let mut expr = self.parse_additive()?;
+
+        while let Some(op) = match &self.current().token_type {
+            TokenType::Eq => Some(BinaryOperator::Eq),
+            TokenType::Ne => Some(BinaryOperator::Ne),
+            TokenType::Lt => Some(BinaryOperator::Lt),
+            TokenType::Gt => Some(BinaryOperator::Gt),
+            TokenType::Le => Some(BinaryOperator::Le),
+            TokenType::Ge => Some(BinaryOperator::Ge),
+            _ => None,
+        } {
+            self.advance();
+            let right = Box::new(self.parse_additive()?);
+            expr = Expression::Binary {
+                op,
+                left: Box::new(expr),
+                right,
+            };
+        }
+
+        Ok(expr)
+    }
+
+    fn parse_additive(&mut self) -> Result<Expression, String> {
+        let mut expr = self.parse_multiplicative()?;
+
+        while let Some(op) = match &self.current().token_type {
+            TokenType::Plus => Some(BinaryOperator::Add),
+            TokenType::Minus => Some(BinaryOperator::Sub),
+            _ => None,
+        } {
+            self.advance();
+            let right = Box::new(self.parse_multiplicative()?);
+            expr = Expression::Binary {
+                op,
+                left: Box::new(expr),
+                right,
+            };
+        }
+
+        Ok(expr)
+    }
+
+    fn parse_multiplicative(&mut self) -> Result<Expression, String> {
+        let mut expr = self.parse_unary()?;
+
+        while let Some(op) = match &self.current().token_type {
+            TokenType::Star => Some(BinaryOperator::Mul),
+            TokenType::Slash => Some(BinaryOperator::Div),
+            _ => None,
+        } {
+            self.advance();
+            let right = Box::new(self.parse_unary()?);
+            expr = Expression::Binary {
+                op,
+                left: Box::new(expr),
+                right,
+            };
+        }
+
+        Ok(expr)
+    }
+
+    fn parse_unary(&mut self) -> Result<Expression, String> {
+        let op = match &self.current().token_type {
+            TokenType::Plus => Some(UnaryOperator::Plus),
+            TokenType::Minus => Some(UnaryOperator::Minus),
+            _ => None,
+        };
+
+        if let Some(op) = op {
+            self.advance();
+            let operand = Box::new(self.parse_unary()?);
+            return Ok(Expression::Unary { op, operand });
+        }
+
+        self.parse_primary()
+    }
+
+    fn parse_primary(&mut self) -> Result<Expression, String> {
+        match &self.current().token_type.clone() {
+            TokenType::Number(n) => {
+                let value = *n;
+                self.advance();
+                Ok(Expression::Number { value })
+            }
+            TokenType::Identifier(name) => {
+                let name = name.clone();
+                self.advance();
+
+                if matches!(self.current().token_type, TokenType::LParen) {
+                    // Function call
+                    self.advance();
+                    let mut args = Vec::new();
+
+                    if !matches!(self.current().token_type, TokenType::RParen) {
+                        args.push(self.parse_expression()?);
+
+                        while matches!(self.current().token_type, TokenType::Comma) {
+                            self.advance();
+                            args.push(self.parse_expression()?);
+                        }
+                    }
+
+                    self.expect(TokenType::RParen)?;
+                    Ok(Expression::Call { name, args })
+                } else {
+                    Ok(Expression::Variable {
+                        name,
+                        expr_type: None,
+                    })
+                }
+            }
+            TokenType::LParen => {
+                self.advance();
+                let expr = self.parse_expression()?;
+                self.expect(TokenType::RParen)?;
+                Ok(expr)
+            }
+            _ => Err(self.error(&format!(
+                "Unexpected token: {:?}",
+                self.current().token_type
+            ))),
+        }
+    }
+}