If statements

Nub.Lang/Nub.Lang/Generation/Generator.cs

@@ -13,6 +13,7 @@ public class Generator
     private readonly Dictionary<string, string> _strings;
     private readonly HashSet<string> _externFuncDefinitions;
     private int _stringIndex;
+    private int _labelIndex;
     
     public Generator(IReadOnlyCollection<DefinitionNode> definitions)
     {
@@ -144,6 +145,9 @@ public class Generator
             case FuncCallStatementNode funcCallStatement:
                 GenerateFuncCall(funcCallStatement.FuncCall, func);
                 break;
+            case IfNode ifStatement:
+                GenerateIf(ifStatement, func);
+                break;
             case ReturnNode @return:
                 GenerateReturn(@return, func);
                 break;
@@ -161,6 +165,33 @@ public class Generator
         }
     }
 
+    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)
@@ -474,4 +505,9 @@ public class Generator
                 
         _builder.AppendLine("    syscall");
     }
+
+    private string CreateLabel()
+    {
+        return $"label{++_labelIndex}";
+    }
 }

Nub.Lang/Nub.Lang/Generation/SymbolTable.cs

@@ -21,11 +21,37 @@ public class SymbolTable
     
     public void DefineFunc(ExternFuncDefinitionNode externFuncDefinition)
     {
+        var existing = _funcDefinitions
+            .FirstOrDefault(f => f
+                .SignatureMatches
+                (
+                    externFuncDefinition.Name, 
+                    externFuncDefinition.Parameters.Select(p => p.Type).ToList()
+                ));
+        
+        if (existing != null)
+        {
+            throw new Exception($"Func {existing} is already defined");
+        }
+        
         _funcDefinitions.Add(new ExternFunc(externFuncDefinition.Name, externFuncDefinition.Name, externFuncDefinition.Parameters, externFuncDefinition.ReturnType));
     }
     
     public void DefineFunc(LocalFuncDefinitionNode localFuncDefinition)
     {
+        var existing = _funcDefinitions
+            .FirstOrDefault(f => f
+                .SignatureMatches
+                (
+                    localFuncDefinition.Name, 
+                    localFuncDefinition.Parameters.Select(p => p.Type).ToList()
+                ));
+        
+        if (existing != null)
+        {
+            throw new Exception($"Func {existing} is already defined");
+        }
+        
         var startLabel = $"func{++_labelIndex}";
         var endLabel = $"func_end{_labelIndex}";
         _funcDefinitions.Add(new LocalFunc(localFuncDefinition.Name, startLabel, endLabel, localFuncDefinition.Parameters, localFuncDefinition.ReturnType, _globalVariables.Concat<Variable>(ResolveFuncVariables(localFuncDefinition)).ToList()));
@@ -56,7 +82,7 @@ public class SymbolTable
     
     public Func ResolveFunc(string name, IReadOnlyCollection<Type> parameterTypes)
     {
-        var func = _funcDefinitions.FirstOrDefault(f => f.Name == name && f.Parameters.Count == parameterTypes.Count && f.Parameters.Where((p, i) => p.Type == parameterTypes.ElementAt(i)).Count() == parameterTypes.Count);
+        var func = _funcDefinitions.FirstOrDefault(f => f.SignatureMatches(name, parameterTypes));
         if (func == null)
         {
             throw new Exception($"Func {name}({string.Join(", ", parameterTypes)}) is not defined");
@@ -115,7 +141,7 @@ public class GlobalVariable(string name, Type type, string identifier) : Variabl
 
 public abstract class Func
 {
-    public Func(string name, string startLabel, IReadOnlyCollection<FuncParameter> parameters, Optional<Type> returnType)
+    protected Func(string name, string startLabel, IReadOnlyCollection<FuncParameter> parameters, Optional<Type> returnType)
     {
         Name = name;
         Parameters = parameters;
@@ -127,6 +153,13 @@ public abstract class Func
     public string StartLabel { get; }
     public IReadOnlyCollection<FuncParameter> Parameters { get; }
     public Optional<Type> ReturnType { get; }
+
+    public bool SignatureMatches(string name, IReadOnlyCollection<Type> parameterTypes)
+    {
+        return Name == name 
+               && Parameters.Count == parameterTypes.Count 
+               && Parameters.Where((p, i) => p.Type == parameterTypes.ElementAt(i)).Count() == parameterTypes.Count;
+    }
 }
 
 public class ExternFunc : Func

Nub.Lang/Nub.Lang/Input/program.nub

@@ -4,12 +4,45 @@ let STD_OUT = 1;
 let STD_ERR = 2;
 
 func main() {
-    print("test\n");
+    println("test");
+    println(true);
+    
+    if true {
+        println("1");
+    } else if false {
+        println("2");
+    } else if true {
+        println("3");
+    } else {
+        println("4");
+    }
 }
 
 func print(msg: String) {
     syscall(SYS_WRITE, STD_OUT, msg, strlen(msg));
 }
 
+func print(value: bool) {
+    if value {
+        print("true");
+    } else {
+        print("false");
+    }
+}
+
+func println() {
+    print("\n");
+}
+
+func println(msg: String) {
+    print(msg);
+    println();
+}
+
+func println(value: bool) {
+    print(value);
+    println();
+}
+
 extern func strlen(msg: String): int64;
 extern func strcmp(a: String, b: String): bool;

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

@@ -10,6 +10,8 @@ public class Lexer
         ["extern"] = Symbol.Extern,
         ["return"] = Symbol.Return,
         ["let"] = Symbol.Let,
+        ["if"] = Symbol.If,
+        ["else"] = Symbol.Else,
     };
 
     private static readonly Dictionary<char[], Symbol> Chians = new()
@@ -80,6 +82,11 @@ public class Lexer
             {
                 return new SymbolToken(keywordSymbol);
             }
+            
+            if (buffer is "true" or "false")
+            {
+                return new LiteralToken(new PrimitiveType(PrimitiveTypeKind.Bool), buffer);
+            }
 
             return new IdentifierToken(buffer);
         }

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

@@ -12,6 +12,8 @@ public enum Symbol
     Func,
     Return,
     Let,
+    If,
+    Else,
     Semicolon,
     Colon,
     OpenParen,

Nub.Lang/Nub.Lang/Nub.Lang.csproj

@@ -8,7 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-      <PackageReference Include="Nub.Core" Version="1.0.0" />
+      <PackageReference Include="Nub.Core" Version="1.0.1" />
     </ItemGroup>
 
 </Project>

Nub.Lang/Nub.Lang/Parsing/IfNode.cs

@@ -0,0 +1,10 @@
+using Nub.Core;
+
+namespace Nub.Lang.Parsing;
+
+public class IfNode(ExpressionNode condition, BlockNode body, Optional<Variant<IfNode, BlockNode>> @else) : StatementNode
+{
+    public ExpressionNode Condition { get; } = condition;
+    public BlockNode Body { get; } = body;
+    public Optional<Variant<IfNode, BlockNode>> Else { get; } = @else;
+}

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

@@ -154,22 +154,15 @@ public class Parser
                 {
                     case Symbol.Return:
                     {
-                        var value = Optional<ExpressionNode>.Empty();
+                        return ParseReturn();
-                        if (!TryExpectSymbol(Symbol.Semicolon))
-                        {
-                            value = ParseExpression();
-                            ExpectSymbol(Symbol.Semicolon);
-                        }
-
-                        return new ReturnNode(value);
                     }
                     case Symbol.Let:
                     {
-                        var name = ExpectIdentifier().Value;
+                        return ParseVariableAssignment();
-                        ExpectSymbol(Symbol.Assign);
+                    }
-                        var value = ParseExpression();
+                    case Symbol.If:
-                        ExpectSymbol(Symbol.Semicolon);
+                    {
-                        return new VariableAssignmentNode(name, value);
+                        return ParseIf();
                     }
                     default:
                     {
@@ -184,6 +177,44 @@ public class Parser
         }
     }
 
+    private ReturnNode ParseReturn()
+    {
+        var value = Optional<ExpressionNode>.Empty();
+        if (!TryExpectSymbol(Symbol.Semicolon))
+        {
+            value = ParseExpression();
+            ExpectSymbol(Symbol.Semicolon);
+        }
+
+        return new ReturnNode(value);
+    }
+
+    private VariableAssignmentNode ParseVariableAssignment()
+    {
+        var name = ExpectIdentifier().Value;
+        ExpectSymbol(Symbol.Assign);
+        var value = ParseExpression();
+        ExpectSymbol(Symbol.Semicolon);
+        
+        return new VariableAssignmentNode(name, value);
+    }
+
+    private IfNode ParseIf()
+    {
+        var condition = ParseExpression();
+        var body = ParseBlock();
+
+        var elseStatement = Optional<Variant<IfNode, BlockNode>>.Empty();
+        if (TryExpectSymbol(Symbol.Else))
+        {
+            elseStatement = TryExpectSymbol(Symbol.If)
+                ? (Variant<IfNode, BlockNode>)ParseIf()
+                : (Variant<IfNode, BlockNode>)ParseBlock();
+        }
+                        
+        return new IfNode(condition, body, elseStatement);
+    }
+
     private ExpressionNode ParseExpression(int precedence = 0)
     {
         var left = ParsePrimaryExpression();

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

@@ -82,6 +82,9 @@ public class ExpressionTyper
             case FuncCallStatementNode funcCall:
                 PopulateFuncCallStatement(funcCall);
                 break;
+            case IfNode ifStatement:
+                PopulateIf(ifStatement);
+                break;
             case ReturnNode returnNode:
                 PopulateReturn(returnNode);
                 break;
@@ -107,6 +110,20 @@ public class ExpressionTyper
         }
     }
 
+    private void PopulateIf(IfNode ifStatement)
+    {
+        PopulateExpression(ifStatement.Condition);
+        PopulateBlock(ifStatement.Body);
+        if (ifStatement.Else.HasValue)
+        {
+            ifStatement.Else.Value.Match
+            (
+                PopulateIf,
+                PopulateBlock
+            );
+        }
+    }
+
     private void PopulateSyscallStatement(SyscallStatementNode syscall)
     {
         foreach (var parameter in syscall.Syscall.Parameters)