...

Nub.Lang/Nub.Lang/Backend/Custom/ExpressionGenerator.cs

@@ -3,220 +3,18 @@ using Nub.Lang.Frontend.Parsing;
 
 namespace Nub.Lang.Backend.Custom;
 
-public class CustomGenerator
+public class ExpressionGenerator
 {
-    private const string Entrypoint = "main";
-    
-    private readonly IReadOnlyCollection<DefinitionNode> _definitions;
-    private readonly SymbolTable _symbolTable;
     private readonly StringBuilder _builder;
-    private readonly Dictionary<string, string> _strings;
+    private readonly SymbolTable _symbolTable;
-    private readonly HashSet<string> _externFuncDefinitions;
-    private int _stringIndex;
-    private int _labelIndex;
 
-    public CustomGenerator(IReadOnlyCollection<DefinitionNode> definitions)
+    public ExpressionGenerator(SymbolTable symbolTable, StringBuilder builder)
     {
-        _strings = [];
+        _symbolTable = symbolTable;
-        _definitions = definitions;
+        _builder = builder;
-        _builder = new StringBuilder();
-        _externFuncDefinitions = ["strcmp"];
-        _symbolTable = new SymbolTable(definitions.OfType<GlobalVariableDefinitionNode>().ToList());
-        
-        foreach (var funcDefinitionNode in definitions.OfType<ExternFuncDefinitionNode>())
-        {
-            _symbolTable.DefineFunc(funcDefinitionNode);
-            _externFuncDefinitions.Add(_symbolTable.ResolveExternFunc(funcDefinitionNode.Name, funcDefinitionNode.Parameters.Select(p => p.Type).ToList()).StartLabel);
-        }
-        foreach (var funcDefinitionNode in definitions.OfType<LocalFuncDefinitionNode>())
-        {
-            _symbolTable.DefineFunc(funcDefinitionNode);
-        }
     }
     
-    public string Generate()
+    public void GenerateExpression(ExpressionNode expression, LocalFunc func)
-    {
-        _builder.AppendLine("global _start");
-        
-        foreach (var externFuncDefinition in _externFuncDefinitions)
-        {
-            _builder.AppendLine($"extern {externFuncDefinition}");
-        }
-        
-        _builder.AppendLine();
-        _builder.AppendLine("section .bss");
-        foreach (var globalVariable in _definitions.OfType<GlobalVariableDefinitionNode>())
-        {
-            var symbol = _symbolTable.ResolveGlobalVariable(globalVariable.Name);
-            _builder.AppendLine($"    {symbol.Identifier}: resq 1 ; {globalVariable.Name}");
-        }
-
-        _builder.AppendLine();
-        _builder.AppendLine("section .text");
-        _builder.AppendLine("_start:");
-        
-        var main = _symbolTable.ResolveLocalFunc(Entrypoint, []);
-        
-        _builder.AppendLine("    ; Initialize global variables");
-        foreach (var globalVariable in _definitions.OfType<GlobalVariableDefinitionNode>())
-        {
-            var symbol = _symbolTable.ResolveGlobalVariable(globalVariable.Name);
-            GenerateExpression(globalVariable.Value, main);
-            _builder.AppendLine($"    mov [{symbol.Identifier}], rax");
-        }
-
-        _builder.AppendLine();
-        _builder.AppendLine($"    ; Call entrypoint {Entrypoint}");
-        _builder.AppendLine($"    call {main.StartLabel}");
-
-        _builder.AppendLine();
-        _builder.AppendLine(main.ReturnType.HasValue
-            ? "    mov rdi, rax ; Exit with return value of entrypoint"
-            : "    mov rdi, 0 ; Exit with default status code 0");
-        _builder.AppendLine("    mov rax, 60");
-        _builder.AppendLine("    syscall");
-
-        foreach (var funcDefinition in _definitions.OfType<LocalFuncDefinitionNode>())
-        {
-            _builder.AppendLine();
-            GenerateFuncDefinition(funcDefinition);
-        }
-        
-        _builder.AppendLine();
-        _builder.AppendLine("section .data");
-        foreach (var str in _strings)
-        {
-            _builder.AppendLine($"{str.Key}: db `{str.Value}`, 0");
-        }
-        
-        return _builder.ToString();
-    }
-
-    private void GenerateFuncDefinition(LocalFuncDefinitionNode node)
-    {
-        var func = _symbolTable.ResolveLocalFunc(node.Name, node.Parameters.Select(p => p.Type).ToList());
-        
-        _builder.AppendLine($"; {node.ToString()}");
-        _builder.AppendLine($"{func.StartLabel}:");
-        _builder.AppendLine("    ; Set up stack frame");
-        _builder.AppendLine("    push rbp");
-        _builder.AppendLine("    mov rbp, rsp");
-        _builder.AppendLine($"    sub rsp, {func.StackAllocation}");
-        
-        string[] registers = ["rdi", "rsi", "rdx", "rcx", "r8", "r9"];
-        
-        _builder.AppendLine("    ; Body");
-        for (var i = 0; i < func.Parameters.Count; i++)
-        {
-            var parameter = func.ResolveLocalVariable(func.Parameters.ElementAt(i).Name);
-            if (i < registers.Length)
-            {
-                _builder.AppendLine($"    mov [rbp - {parameter.Offset}], {registers[i]}");
-            }
-            else
-            {
-                var stackOffset = 16 + (i - registers.Length) * 8;
-                _builder.AppendLine($"    mov rax, [rbp + {stackOffset}]");
-                _builder.AppendLine($"    mov [rbp - {parameter.Offset}], rax");
-            }
-        }
-        
-        GenerateBlock(node.Body, func);
-
-        _builder.AppendLine($"{func.EndLabel}:");
-        _builder.AppendLine("    ; Clean up stack frame");
-        _builder.AppendLine("    mov rsp, rbp");
-        _builder.AppendLine("    pop rbp");
-        _builder.AppendLine("    ret");
-    }
-    
-    private void GenerateBlock(BlockNode block, LocalFunc func)
-    {
-        foreach (var statement in block.Statements)
-        {
-            GenerateStatement(statement, func);
-        }
-    }
-
-    private void GenerateStatement(StatementNode statement, LocalFunc func)
-    {
-        switch (statement)
-        {
-            case FuncCallStatementNode funcCallStatement:
-                GenerateFuncCall(funcCallStatement.FuncCall, func);
-                break;
-            case IfNode ifStatement:
-                GenerateIf(ifStatement, func);
-                break;
-            case ReturnNode @return:
-                GenerateReturn(@return, func);
-                break;
-            case SyscallStatementNode syscallStatement:
-                GenerateSyscall(syscallStatement.Syscall, func);
-                break;
-            case VariableAssignmentNode variableAssignment:
-                GenerateVariableAssignment(variableAssignment, func);
-                break;
-            case VariableReassignmentNode variableReassignment:
-                GenerateVariableReassignment(variableReassignment, func);
-                break;
-            default:
-                throw new ArgumentOutOfRangeException(nameof(statement));
-        }
-    }
-
-    private void GenerateIf(IfNode ifStatement, LocalFunc func)
-    {
-        var endLabel = CreateLabel();
-        GenerateIf(ifStatement, endLabel, func);
-        _builder.AppendLine($"{endLabel}:");
-    }
-    
-    private void GenerateIf(IfNode ifStatement, string endLabel, LocalFunc func)
-    {
-        var nextLabel = CreateLabel();
-        GenerateExpression(ifStatement.Condition, func);
-        _builder.AppendLine("    cmp rax, 0");
-        _builder.AppendLine($"    je {nextLabel}");
-        GenerateBlock(ifStatement.Body, func);
-        _builder.AppendLine($"    jmp {endLabel}");
-        _builder.AppendLine($"{nextLabel}:");
-        
-        if (ifStatement.Else.HasValue)
-        {
-            ifStatement.Else.Value.Match
-            (
-                elseIfStatement => GenerateIf(elseIfStatement, endLabel, func),
-                elseStatement => GenerateBlock(elseStatement, func)
-            );
-        }
-    }
-
-    private void GenerateReturn(ReturnNode @return, LocalFunc func)
-    {
-        if (@return.Value.HasValue)
-        {
-            GenerateExpression(@return.Value.Value, func);
-        }
-
-        _builder.AppendLine($"    jmp {func.EndLabel}");
-    }
-
-    private void GenerateVariableAssignment(VariableAssignmentNode variableAssignment, LocalFunc func)
-    {
-        var variable = func.ResolveLocalVariable(variableAssignment.Name);
-        GenerateExpression(variableAssignment.Value, func);
-        _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
-    }
-
-    private void GenerateVariableReassignment(VariableReassignmentNode variableReassignment, LocalFunc func)
-    {
-        var variable = func.ResolveLocalVariable(variableReassignment.Name);
-        GenerateExpression(variableReassignment.Value, func);
-        _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
-    }
-
-    private void GenerateExpression(ExpressionNode expression, LocalFunc func)
     {
         switch (expression)
         {
@@ -431,8 +229,8 @@ public class CustomGenerator
             }
             case StringType:
             {
-                var ident = $"string{++_stringIndex}";
+                var ident = _symbolTable.LabelFactory.Create();
-                _strings.Add(ident, literal.Literal);
+                _symbolTable.DefineString(ident, literal.Literal);
                 _builder.AppendLine($"    mov rax, {ident}");
                 break;
             }
@@ -462,7 +260,7 @@ public class CustomGenerator
         }
     }
 
-    private void GenerateFuncCall(FuncCall funcCall, LocalFunc func)
+    public void GenerateFuncCall(FuncCall funcCall, LocalFunc func)
     {
         var symbol = _symbolTable.ResolveFunc(funcCall.Name, funcCall.Parameters.Select(p => p.Type).ToList());
         string[] registers = ["rdi", "rsi", "rdx", "rcx", "r8", "r9"];
@@ -488,7 +286,7 @@ public class CustomGenerator
         }
     }
 
-    private void GenerateSyscall(Syscall syscall, LocalFunc func)
+    public void GenerateSyscall(Syscall syscall, LocalFunc func)
     {
         string[] registers = ["rax", "rdi", "rsi", "rdx", "r10", "r8", "r9"];
 
@@ -505,9 +303,4 @@ public class CustomGenerator
                 
         _builder.AppendLine("    syscall");
     }
-
-    private string CreateLabel()
-    {
-        return $"label{++_labelIndex}";
-    }
 }

Nub.Lang/Nub.Lang/Backend/Custom/FuncGenerator.cs

@@ -0,0 +1,146 @@
+using System.Text;
+using Nub.Lang.Frontend.Parsing;
+
+namespace Nub.Lang.Backend.Custom;
+
+public class FuncGenerator
+{
+    private readonly SymbolTable _symbolTable;
+    private readonly ExpressionGenerator _expressionGenerator;
+    private readonly StringBuilder _builder;
+
+    public FuncGenerator(SymbolTable symbolTable, StringBuilder builder, ExpressionGenerator expressionGenerator)
+    {
+        _symbolTable = symbolTable;
+        _builder = builder;
+        _expressionGenerator = expressionGenerator;
+    }
+
+    public string GenerateFuncDefinition(LocalFuncDefinitionNode node)
+    {
+        var func = _symbolTable.ResolveLocalFunc(node.Name, node.Parameters.Select(p => p.Type).ToList());
+        
+        _builder.AppendLine($"; {node.ToString()}");
+        _builder.AppendLine($"{func.StartLabel}:");
+        _builder.AppendLine("    ; Set up stack frame");
+        _builder.AppendLine("    push rbp");
+        _builder.AppendLine("    mov rbp, rsp");
+        _builder.AppendLine($"    sub rsp, {func.StackAllocation}");
+        
+        string[] registers = ["rdi", "rsi", "rdx", "rcx", "r8", "r9"];
+        
+        _builder.AppendLine("    ; Body");
+        for (var i = 0; i < func.Parameters.Count; i++)
+        {
+            var parameter = func.ResolveLocalVariable(func.Parameters.ElementAt(i).Name);
+            if (i < registers.Length)
+            {
+                _builder.AppendLine($"    mov [rbp - {parameter.Offset}], {registers[i]}");
+            }
+            else
+            {
+                var stackOffset = 16 + (i - registers.Length) * 8;
+                _builder.AppendLine($"    mov rax, [rbp + {stackOffset}]");
+                _builder.AppendLine($"    mov [rbp - {parameter.Offset}], rax");
+            }
+        }
+        
+        GenerateBlock(node.Body, func);
+
+        _builder.AppendLine($"{func.EndLabel}:");
+        _builder.AppendLine("    ; Clean up stack frame");
+        _builder.AppendLine("    mov rsp, rbp");
+        _builder.AppendLine("    pop rbp");
+        _builder.AppendLine("    ret");
+
+        var result = _builder.ToString();
+        _builder.Clear();
+        return result;
+    }
+    
+    private void GenerateBlock(BlockNode block, LocalFunc func)
+    {
+        foreach (var statement in block.Statements)
+        {
+            GenerateStatement(statement, func);
+        }
+    }
+
+    private void GenerateStatement(StatementNode statement, LocalFunc func)
+    {
+        switch (statement)
+        {
+            case FuncCallStatementNode funcCallStatement:
+                _expressionGenerator.GenerateFuncCall(funcCallStatement.FuncCall, func);
+                break;
+            case IfNode ifStatement:
+                GenerateIf(ifStatement, func);
+                break;
+            case ReturnNode @return:
+                GenerateReturn(@return, func);
+                break;
+            case SyscallStatementNode syscallStatement:
+                _expressionGenerator.GenerateSyscall(syscallStatement.Syscall, func);
+                break;
+            case VariableAssignmentNode variableAssignment:
+                GenerateVariableAssignment(variableAssignment, func);
+                break;
+            case VariableReassignmentNode variableReassignment:
+                GenerateVariableReassignment(variableReassignment, func);
+                break;
+            default:
+                throw new ArgumentOutOfRangeException(nameof(statement));
+        }
+    }
+
+    private void GenerateIf(IfNode ifStatement, LocalFunc func)
+    {
+        var endLabel = _symbolTable.LabelFactory.Create();
+        GenerateIf(ifStatement, endLabel, func);
+        _builder.AppendLine($"{endLabel}:");
+    }
+    
+    private void GenerateIf(IfNode ifStatement, string endLabel, LocalFunc func)
+    {
+        var nextLabel = _symbolTable.LabelFactory.Create();
+        _expressionGenerator.GenerateExpression(ifStatement.Condition, func);
+        _builder.AppendLine("    cmp rax, 0");
+        _builder.AppendLine($"    je {nextLabel}");
+        GenerateBlock(ifStatement.Body, func);
+        _builder.AppendLine($"    jmp {endLabel}");
+        _builder.AppendLine($"{nextLabel}:");
+        
+        if (ifStatement.Else.HasValue)
+        {
+            ifStatement.Else.Value.Match
+            (
+                elseIfStatement => GenerateIf(elseIfStatement, endLabel, func),
+                elseStatement => GenerateBlock(elseStatement, func)
+            );
+        }
+    }
+
+    private void GenerateReturn(ReturnNode @return, LocalFunc func)
+    {
+        if (@return.Value.HasValue)
+        {
+            _expressionGenerator.GenerateExpression(@return.Value.Value, func);
+        }
+
+        _builder.AppendLine($"    jmp {func.EndLabel}");
+    }
+
+    private void GenerateVariableAssignment(VariableAssignmentNode variableAssignment, LocalFunc func)
+    {
+        var variable = func.ResolveLocalVariable(variableAssignment.Name);
+        _expressionGenerator.GenerateExpression(variableAssignment.Value, func);
+        _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
+    }
+
+    private void GenerateVariableReassignment(VariableReassignmentNode variableReassignment, LocalFunc func)
+    {
+        var variable = func.ResolveLocalVariable(variableReassignment.Name);
+        _expressionGenerator.GenerateExpression(variableReassignment.Value, func);
+        _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
+    }
+}

Nub.Lang/Nub.Lang/Backend/Custom/Generator.cs

@@ -0,0 +1,123 @@
+using System.Text;
+using Nub.Lang.Frontend.Parsing;
+
+namespace Nub.Lang.Backend.Custom;
+
+public class Generator
+{
+    private const string Entrypoint = "main";
+    
+    private readonly List<DefinitionNode> _definitions;
+    private readonly SymbolTable _symbolTable;
+    private readonly StringBuilder _builder;
+    private readonly HashSet<string> _externFuncDefinitions;
+    private readonly ExpressionGenerator _expressionGenerator;
+    private readonly FuncGenerator _funcGenerator;
+    
+    public Generator(FileNode file, Dictionary<string, FileNode> deps)
+    {
+        _definitions = [];
+        _builder = new StringBuilder();
+        _externFuncDefinitions = ["strcmp"];
+        _symbolTable = new SymbolTable();
+        _expressionGenerator = new ExpressionGenerator(_symbolTable, _builder);
+        _funcGenerator = new FuncGenerator(_symbolTable, _builder, _expressionGenerator);
+        
+        ResolveGlobalVariables(file, deps);
+        ResolveDefinitions(file, deps);
+    }
+
+    private void ResolveGlobalVariables(FileNode file, Dictionary<string, FileNode> deps)
+    {
+        
+        foreach (var globalVariableDefinition in file.Definitions.OfType<GlobalVariableDefinitionNode>())
+        {
+            _symbolTable.DefineGlobalVariable(globalVariableDefinition);
+            _definitions.Add(globalVariableDefinition);
+        }
+        
+        foreach (var include in file.Includes)
+        {
+            ResolveGlobalVariables(deps[include], deps);
+        }
+    }
+    
+    private void ResolveDefinitions(FileNode file, Dictionary<string, FileNode> deps)
+    {
+        foreach (var funcDefinitionNode in file.Definitions.OfType<ExternFuncDefinitionNode>())
+        {
+            _symbolTable.DefineFunc(funcDefinitionNode);
+            _definitions.Add(funcDefinitionNode);
+            _externFuncDefinitions.Add(_symbolTable.ResolveExternFunc(funcDefinitionNode.Name, funcDefinitionNode.Parameters.Select(p => p.Type).ToList()).StartLabel);
+        }
+        
+        foreach (var funcDefinitionNode in file.Definitions.OfType<LocalFuncDefinitionNode>())
+        {
+            _symbolTable.DefineFunc(funcDefinitionNode);
+            _definitions.Add(funcDefinitionNode);
+        }
+        
+        foreach (var include in file.Includes)
+        {
+            ResolveDefinitions(deps[include], deps);
+        }
+    }
+
+    public string Generate()
+    {
+        _builder.AppendLine("global _start");
+        
+        foreach (var externFuncDefinition in _externFuncDefinitions)
+        {
+            _builder.AppendLine($"extern {externFuncDefinition}");
+        }
+        
+        _builder.AppendLine();
+        _builder.AppendLine("section .bss");
+        foreach (var globalVariable in _definitions.OfType<GlobalVariableDefinitionNode>())
+        {
+            var symbol = _symbolTable.ResolveGlobalVariable(globalVariable.Name);
+            _builder.AppendLine($"    {symbol.Identifier}: resq 1 ; {globalVariable.Name}");
+        }
+
+        _builder.AppendLine();
+        _builder.AppendLine("section .text");
+        _builder.AppendLine("_start:");
+        
+        var main = _symbolTable.ResolveLocalFunc(Entrypoint, []);
+        
+        _builder.AppendLine("    ; Initialize global variables");
+        foreach (var globalVariable in _definitions.OfType<GlobalVariableDefinitionNode>())
+        {
+            var symbol = _symbolTable.ResolveGlobalVariable(globalVariable.Name);
+            _expressionGenerator.GenerateExpression(globalVariable.Value, main);
+            _builder.AppendLine($"    mov [{symbol.Identifier}], rax");
+        }
+
+        _builder.AppendLine();
+        _builder.AppendLine($"    ; Call entrypoint {Entrypoint}");
+        _builder.AppendLine($"    call {main.StartLabel}");
+
+        _builder.AppendLine();
+        _builder.AppendLine(main.ReturnType.HasValue
+            ? "    mov rdi, rax ; Exit with return value of entrypoint"
+            : "    mov rdi, 0 ; Exit with default status code 0");
+        _builder.AppendLine("    mov rax, 60");
+        _builder.AppendLine("    syscall");
+
+        foreach (var funcDefinition in _definitions.OfType<LocalFuncDefinitionNode>())
+        {
+            _builder.AppendLine();
+            _builder.AppendLine(_funcGenerator.GenerateFuncDefinition(funcDefinition));
+        }
+        
+        _builder.AppendLine();
+        _builder.AppendLine("section .data");
+        foreach (var str in _symbolTable.Strings)
+        {
+            _builder.AppendLine($"{str.Key}: db `{str.Value}`, 0");
+        }
+        
+        return _builder.ToString();
+    }
+}

Nub.Lang/Nub.Lang/Backend/Custom/SymbolTable.cs

@@ -7,16 +7,20 @@ public class SymbolTable
 {
     private readonly List<Func> _funcDefinitions = [];
     private readonly List<GlobalVariable> _globalVariables = [];
-    private int _labelIndex;
+    private int _globalVariableIndex;
+    public LabelFactory LabelFactory { get; } = new();
     
-    public SymbolTable(IReadOnlyCollection<GlobalVariableDefinitionNode> globalVariableDefinitions)
+    public readonly Dictionary<string, string> Strings = [];
+
+    public void DefineString(string label, string value)
     {
-        var globalVariableIndex = 0;
+        Strings.Add(label, value);
-        foreach (var globalVariable in globalVariableDefinitions)
+    }
-        {
+    
-            var identifier = $"variable{++globalVariableIndex}";
+    public void DefineGlobalVariable(GlobalVariableDefinitionNode globalVariableDefinition)
-            _globalVariables.Add(new GlobalVariable(globalVariable.Name, globalVariable.Value.Type, identifier));
+    {
-        }
+        var identifier = $"variable{++_globalVariableIndex}";
+        _globalVariables.Add(new GlobalVariable(globalVariableDefinition.Name, globalVariableDefinition.Value.Type, identifier));
     }
     
     public void DefineFunc(ExternFuncDefinitionNode externFuncDefinition)
@@ -52,8 +56,8 @@ public class SymbolTable
             throw new Exception($"Func {existing} is already defined");
         }
         
-        var startLabel = $"func{++_labelIndex}";
+        var startLabel = LabelFactory.Create();
-        var endLabel = $"func_end{_labelIndex}";
+        var endLabel = LabelFactory.Create();
         _funcDefinitions.Add(new LocalFunc(localFuncDefinition.Name, startLabel, endLabel, localFuncDefinition.Parameters, localFuncDefinition.ReturnType, _globalVariables.Concat<Variable>(ResolveFuncVariables(localFuncDefinition)).ToList()));
     }
     
@@ -210,3 +214,10 @@ public class LocalFunc : Func
     
     public override string ToString() => $"{Name}({string.Join(", ", Parameters.Select(p => p.ToString()))}){(ReturnType.HasValue ? ": " + ReturnType.Value : "")}";
 }
+
+public class LabelFactory
+{
+    private int _index;
+    
+    public string Create() => $"label{++_index}";
+}

Nub.Lang/Nub.Lang/Frontend/Lexing/Lexer.cs

@@ -9,6 +9,7 @@ public class Lexer
         ["func"] = Symbol.Func,
         ["extern"] = Symbol.Extern,
         ["return"] = Symbol.Return,
+        ["include"] = Symbol.Include,
         ["let"] = Symbol.Let,
         ["if"] = Symbol.If,
         ["else"] = Symbol.Else,

Nub.Lang/Nub.Lang/Frontend/Lexing/SymbolToken.cs

@@ -8,6 +8,7 @@ public class SymbolToken(Symbol symbol) : Token
 public enum Symbol
 {
     Whitespace,
+    Include,
     Extern,
     Func,
     Return,

Nub.Lang/Nub.Lang/Frontend/Parsing/FileNode.cs

@@ -0,0 +1,7 @@
+namespace Nub.Lang.Frontend.Parsing;
+
+public class FileNode(IReadOnlyCollection<string> includes, IReadOnlyCollection<DefinitionNode> definitions) : Node
+{
+    public IReadOnlyCollection<string> Includes { get; } = includes;
+    public IReadOnlyCollection<DefinitionNode> Definitions { get; } = definitions;
+}

Nub.Lang/Nub.Lang/Frontend/Parsing/Parser.cs

@@ -14,16 +14,30 @@ public class Parser
         _tokens = tokens.ToArray();
     }
 
-    public IReadOnlyCollection<DefinitionNode> Parse()
+    public FileNode ParseFile(string relativePath)
     {
         _index = 0;
         List<DefinitionNode> definitions = [];
+        List<string> includes = [];
+
+        while (TryExpectSymbol(Symbol.Include))
+        {
+            var name = ExpectLiteral();
+            if (name.Type is not StringType)
+            {
+                throw new Exception("Using statements must have a string literal value");
+            }
+
+            TryExpectSymbol(Symbol.Semicolon);
+            includes.Add(name.Value);
+        }
+        
         while (Peek().HasValue)
         {
             definitions.Add(ParseDefinition());
         }
 
-        return definitions;
+        return new FileNode(includes, definitions);
     }
 
     private DefinitionNode ParseDefinition()

Nub.Lang/Nub.Lang/Frontend/Typing/ExpressionTyper.cs

@@ -13,25 +13,39 @@ public class Func(string name, IReadOnlyCollection<FuncParameter> parameters, Op
 
 public class ExpressionTyper
 {
-    private readonly IReadOnlyCollection<Func> _functions;
+    private readonly List<Func> _functions;
-    private readonly IReadOnlyCollection<GlobalVariableDefinitionNode> _variableDefinitions;
+    private readonly List<GlobalVariableDefinitionNode> _variableDefinitions;
     private readonly Stack<Variable> _variables;
 
-    public ExpressionTyper(IReadOnlyCollection<DefinitionNode> definitions)
+    public ExpressionTyper(FileNode file, Dictionary<string, FileNode> deps)
     {
-        var functions = definitions
+        _variables = new Stack<Variable>();
+        _functions = [];
+        _variableDefinitions = [];
+        
+        ResolveFunctions(file, deps);
+    }
+
+    private void ResolveFunctions(FileNode file, Dictionary<string, FileNode> deps)
+    {
+        var functions = file.Definitions
             .OfType<LocalFuncDefinitionNode>()
             .Select(f => new Func(f.Name, f.Parameters, f.Body, f.ReturnType))
             .ToList();
         
-        var externFunctions = definitions
+        var externFunctions = file.Definitions
             .OfType<ExternFuncDefinitionNode>()
             .Select(f => new Func(f.Name, f.Parameters, Optional<BlockNode>.Empty(), f.ReturnType))
             .ToList();
         
-        _functions = functions.Concat(externFunctions).ToList();
+        _functions.AddRange(functions);
-        _variableDefinitions = definitions.OfType<GlobalVariableDefinitionNode>().ToList();
+        _functions.AddRange(externFunctions);
-        _variables = new Stack<Variable>();
+        _variableDefinitions.AddRange(file.Definitions.OfType<GlobalVariableDefinitionNode>());
+        
+        foreach (var include in file.Includes)
+        {
+            ResolveFunctions(deps[include], deps);
+        }
     }
 
     public void Populate()

Nub.Lang/Nub.Lang/Program.cs

@@ -1,20 +1,46 @@
-using Nub.Lang.Backend.Custom;
+using System.Diagnostics;
+using Nub.Lang.Backend.Custom;
 using Nub.Lang.Frontend.Lexing;
 using Nub.Lang.Frontend.Parsing;
 using Nub.Lang.Frontend.Typing;
 
-var src = File.ReadAllText(args[0]);
+var rootPath = Path.GetDirectoryName(args[0]);
+var rootFileName = Path.GetFileName(args[0]);
+Debug.Assert(rootPath != null && rootFileName != null);
 
-var lexer = new Lexer(src);
+Dictionary<string, FileNode> files = [];
-var tokens = lexer.Lex();
 
-var parser = new Parser(tokens);
+Queue<string> queue = [];
-var definitions = parser.Parse();
+queue.Enqueue(rootFileName);
 
-var typer = new ExpressionTyper(definitions);
+while (queue.TryDequeue(out var path))
-typer.Populate();
+{
+    var src = File.ReadAllText(Path.Combine(rootPath, path));
     
-var generator = new CustomGenerator(definitions);
+    var lexer = new Lexer(src);
+    var tokens = lexer.Lex();
+    
+    var parser = new Parser(tokens);
+    var file = parser.ParseFile(path);
+    files[path] = file;
+
+    foreach (var include in file.Includes)
+    {
+        if (!files.ContainsKey(include))
+        {
+            queue.Enqueue(include);
+        }
+    }
+}
+
+foreach (var file in files)
+{
+    var typer = new ExpressionTyper(file.Value, files);
+    typer.Populate();
+}
+
+
+var generator = new Generator(files[rootFileName], files);
 var asm = generator.Generate();
 
 Console.WriteLine(asm);

Nub.Lang/Nub.Lang/input/core/print.nub

@@ -1,4 +1,4 @@
-namespace core;
+include "core/string.nub"
 
 let SYS_WRITE = 1;
 let STD_IN = 0;

Nub.Lang/Nub.Lang/input/core/string.asm

@@ -1,4 +1,5 @@
 global strlen
+global strcmp
 section .text
 
 strcmp:
@@ -18,3 +19,14 @@ strcmp:
 .equal:
     mov rax, 1
     ret
+
+strlen:
+    xor rax, rax
+.loop:
+    cmp byte [rdi], 0
+    jz .done
+    inc rax
+    inc rdi
+    jmp .loop
+.done:
+    ret

Nub.Lang/Nub.Lang/input/core/string.nub

@@ -1,3 +1,2 @@
-namespace core;
+extern func strlen(msg: String): int64;
-
 extern func strcmp(a: String, b: String): bool;

Nub.Lang/Nub.Lang/input/core/string/strlen.asm

@@ -1,13 +0,0 @@
-global strlen
-section .text
-
-strlen:
-    xor rax, rax
-.loop:
-    cmp byte [rdi], 0
-    jz .done
-    inc rax
-    inc rdi
-    jmp .loop
-.done:
-    ret

Nub.Lang/Nub.Lang/input/core/string/strlen.nub

@@ -1,3 +0,0 @@
-namespace core;
-
-extern func strlen(msg: String): int64;

Nub.Lang/Nub.Lang/input/program.nub

@@ -1,17 +1,16 @@
-namespace program;
+include "core/print.nub";
-using core;
 
 func main() {
-    core::println("test");
+    println("test");
-    core::println(true);
+    println(true);
     
-    if true {
+    if strlen("1") == 1 {
-        core::println("1");
+        println("1");
     } else if false {
-        core::println("2");
+        println("2");
     } else if true {
-        core::println("3");
+        println("3");
     } else {
-        core::println("4");
+        println("4");
     }
 }

Nub.Lang/Nub.Lang/output/build.sh

@@ -1,6 +1,5 @@
 #!/bin/sh
 nasm -g -felf64 out.asm -o out.o
-nasm -g -felf64 ../input/core/string/strlen.asm -o strlen.o
+nasm -g -felf64 ../input/core/string.asm -o string.o
-nasm -g -felf64 ../input/core/string/strcmp.asm -o strcmp.o
 
-ld -o out out.o strlen.o strcmp.o
+ld -o out out.o string.o