IF ELSE ENDIF

Program.cs

@@ -21,29 +21,43 @@ class Program {
     }
 }
 
-// === AST & TYPES ===
+// === AST ===
 public enum VarType { Int8=1, Int16=2, Int32=3, Byte=4, Bool=5 }
+
 public abstract class StNode {}
 public class ProgramNode : StNode { public List<VarDecl> Vars=new(); public List<Stmt> Stmts=new(); }
 public class VarDecl : StNode { public string Name; public VarType Type; public Expr? Init; }
+
 public abstract class Stmt : StNode {}
 public class AssignStmt : Stmt { public string Target; public Expr Expr; }
+public class IfStmt : Stmt { public Expr Cond; public List<Stmt> ThenStmts=new(); public List<Stmt> ElseStmts=new(); }
+
 public abstract class Expr : StNode {}
 public class IntExpr : Expr { public int Value; public IntExpr(int v){Value=v;} }
 public class VarExpr : Expr { public string Name; public VarExpr(string n){Name=n;} }
 public class BinaryExpr : Expr { public Expr L; public Expr R; public TokType Op; public BinaryExpr(Expr l, TokType op, Expr r){L=l;Op=op;R=r;} }
 
-// === LEXER ===
+// === TOKENIZER ===
-public enum TokType { IDENT, INT, ASSIGN, SEMI, LPAREN, RPAREN, PLUS, MINUS, MUL, DIV, PROGRAM, VAR, END_VAR, END_PROGRAM, EOF }
+public enum TokType {
+    IDENT, INT, ASSIGN, SEMI, LPAREN, RPAREN,
+    PLUS, MINUS, MUL, DIV,
+    LT, GT, LE, GE, EQ, NEQ,
+    IF, THEN, ELSE, END_IF,
+    PROGRAM, VAR, END_VAR, END_PROGRAM,
+    EOF
+}
 public class Token { public TokType Type; public string Text; public Token(TokType t,string s){Type=t;Text=s;} }
+
 public class StLexer {
     private readonly string src; private int i;
     public StLexer(string s){src=s;}
     char Peek()=> i<src.Length?src[i]:'\0';
     char Next()=> i<src.Length?src[i++]:'\0';
+
     public Token NextToken() {
         while (char.IsWhiteSpace(Peek())) Next();
         if (Peek()=='\0') return new Token(TokType.EOF,"");
+
         if (char.IsLetter(Peek())||Peek()=='_') {
             var sb=new StringBuilder();
             while (char.IsLetterOrDigit(Peek())||Peek()=='_') sb.Append(Next());
@@ -53,15 +67,31 @@ public class StLexer {
                 case "VAR": return new Token(TokType.VAR,s);
                 case "END_VAR": return new Token(TokType.END_VAR,s);
                 case "END_PROGRAM": return new Token(TokType.END_PROGRAM,s);
+                case "IF": return new Token(TokType.IF,s);
+                case "THEN": return new Token(TokType.THEN,s);
+                case "ELSE": return new Token(TokType.ELSE,s);
+                case "END_IF": return new Token(TokType.END_IF,s);
                 default: return new Token(TokType.IDENT,s);
             }
         }
+
         if (char.IsDigit(Peek())) {
             var sb=new StringBuilder();
             while (char.IsDigit(Peek())) sb.Append(Next());
             return new Token(TokType.INT,sb.ToString());
         }
+
+        // Operators and symbols
         if (Peek()==':') { Next(); if(Peek()=='='){Next(); return new Token(TokType.ASSIGN,":=");} }
+        if (Peek()=='<') {
+            Next();
+            if (Peek()=='='){Next(); return new Token(TokType.LE,"<=");}
+            if (Peek()=='>'){Next(); return new Token(TokType.NEQ,"<>");}
+            return new Token(TokType.LT,"<");
+        }
+        if (Peek()=='>') { Next(); if (Peek()=='='){Next(); return new Token(TokType.GE,">=");} return new Token(TokType.GT,">"); }
+        if (Peek()=='=') { Next(); return new Token(TokType.EQ,"="); }
+
         char c=Next();
         return c switch {
             ';'=>new Token(TokType.SEMI,";"),
@@ -82,6 +112,7 @@ public class StParser {
     public StParser(string s){lex=new StLexer(s);cur=lex.NextToken();}
     void Next()=>cur=lex.NextToken();
     void Expect(TokType t){ if(cur.Type!=t) throw new Exception($"Expected {t}, got {cur.Type}"); Next(); }
+
     public ProgramNode ParseProgram() {
         var p=new ProgramNode();
         Expect(TokType.PROGRAM);
@@ -96,29 +127,80 @@ public class StParser {
         Expect(TokType.END_PROGRAM);
         return p;
     }
+
     VarDecl ParseVarDecl() {
         string name=cur.Text; Expect(TokType.IDENT);
         string tname=cur.Text.ToLowerInvariant(); Expect(TokType.IDENT);
         VarType vt = tname switch {
             "int8"=>VarType.Int8, "int16"=>VarType.Int16, "int32"=>VarType.Int32,
-            "byte"=>VarType.Byte,"bool"=>VarType.Bool,_=>throw new Exception($"Unknown type {tname}")
+            "byte"=>VarType.Byte, "bool"=>VarType.Bool,
+            _=>throw new Exception($"Unknown type {tname}")
         };
         Expr? init=null;
         if (cur.Type==TokType.ASSIGN){ Next(); init=ParseExpr(); }
         Expect(TokType.SEMI);
         return new VarDecl{Name=name,Type=vt,Init=init};
     }
+
     Stmt ParseStmt() {
+        if (cur.Type==TokType.IF) return ParseIf();
         if (cur.Type==TokType.IDENT) {
             var n=cur.Text; Next(); Expect(TokType.ASSIGN);
             var e=ParseExpr(); Expect(TokType.SEMI);
             return new AssignStmt{Target=n,Expr=e};
         }
-        throw new Exception($"Invalid stmt start {cur.Type}");
+        throw new Exception($"Unexpected token in statement: {cur.Type}");
     }
-    Expr ParseExpr(){return ParseAddSub();}
+
-    Expr ParseAddSub(){var l=ParseMulDiv();while(cur.Type==TokType.PLUS||cur.Type==TokType.MINUS){var op=cur.Type;Next();var r=ParseMulDiv();l=new BinaryExpr(l,op,r);}return l;}
+    IfStmt ParseIf() {
-    Expr ParseMulDiv(){var l=ParsePrimary();while(cur.Type==TokType.MUL||cur.Type==TokType.DIV){var op=cur.Type;Next();var r=ParsePrimary();l=new BinaryExpr(l,op,r);}return l;}
+        Next(); // consume IF
+        var cond = ParseExpr();
+        Expect(TokType.THEN);
+        var ifs = new IfStmt{Cond=cond};
+        while(cur.Type!=TokType.ELSE && cur.Type!=TokType.END_IF)
+            ifs.ThenStmts.Add(ParseStmt());
+        if (cur.Type==TokType.ELSE) {
+            Next();
+            while(cur.Type!=TokType.END_IF)
+                ifs.ElseStmts.Add(ParseStmt());
+        }
+        Expect(TokType.END_IF);
+        Expect(TokType.SEMI);
+        return ifs;
+    }
+
+    Expr ParseExpr() => ParseCompare();
+
+    Expr ParseCompare() {
+        var l=ParseAddSub();
+        while(cur.Type is TokType.LT or TokType.GT or TokType.LE or TokType.GE or TokType.EQ or TokType.NEQ) {
+            var op=cur.Type; Next();
+            var r=ParseAddSub();
+            l=new BinaryExpr(l,op,r);
+        }
+        return l;
+    }
+
+    Expr ParseAddSub() {
+        var l=ParseMulDiv();
+        while(cur.Type==TokType.PLUS||cur.Type==TokType.MINUS){
+            var op=cur.Type;Next();
+            var r=ParseMulDiv();
+            l=new BinaryExpr(l,op,r);
+        }
+        return l;
+    }
+
+    Expr ParseMulDiv() {
+        var l=ParsePrimary();
+        while(cur.Type==TokType.MUL||cur.Type==TokType.DIV){
+            var op=cur.Type;Next();
+            var r=ParsePrimary();
+            l=new BinaryExpr(l,op,r);
+        }
+        return l;
+    }
+
     Expr ParsePrimary() {
         if (cur.Type==TokType.INT){int v=int.Parse(cur.Text);Next();return new IntExpr(v);}
         if (cur.Type==TokType.IDENT){string n=cur.Text;Next();return new VarExpr(n);}
@@ -127,7 +209,7 @@ public class StParser {
     }
 }
 
-// === BYTECODE EMITTER ===
+// === BYTECODE ===
 public class BytecodeEmitter {
     List<int> consts=new(); Dictionary<string,Symbol> syms=new(); List<byte> code=new();
     class Symbol{public string Name;public VarType Type;public int Index;}
@@ -135,19 +217,12 @@ public class BytecodeEmitter {
 
     public void Compile(ProgramNode p){
         int idx=0;
-        // Pass 1: Definiere Variablen (ohne Init)
         foreach(var v in p.Vars)
             syms[v.Name]=new Symbol{Name=v.Name,Type=v.Type,Index=idx++};
 
-        // Pass 2: Generiere Initialisierungscode
+        foreach(var v in p.Vars)
-        foreach(var v in p.Vars){
+            if(v.Init!=null){ EmitExpr(v.Init); EmitByte(0x03); EmitU16((ushort)syms[v.Name].Index); }
-            if(v.Init!=null){
-                EmitExpr(v.Init);
-                EmitByte(0x03); EmitU16((ushort)syms[v.Name].Index);
-            }
-        }
 
-        // Main-Code
         foreach(var s in p.Stmts)
             EmitStmt(s);
 
@@ -155,25 +230,46 @@ public class BytecodeEmitter {
     }
 
     void EmitStmt(Stmt s){
-        if(s is AssignStmt a){
+        switch(s){
+            case AssignStmt a:
                 EmitExpr(a.Expr);
                 EmitByte(0x03); EmitU16((ushort)syms[a.Target].Index);
+                break;
+            case IfStmt iff:
+                EmitExpr(iff.Cond);
+                EmitByte(0x20); // JZ (jump if zero)
+                int jzPos = code.Count; EmitU16(0);
+                foreach(var st in iff.ThenStmts) EmitStmt(st);
+                if (iff.ElseStmts.Count>0){
+                    EmitByte(0x21); // JMP unconditional
+                    int jmpPos = code.Count; EmitU16(0);
+                    PatchJump(jzPos, code.Count);
+                    foreach(var st in iff.ElseStmts) EmitStmt(st);
+                    PatchJump(jmpPos, code.Count);
+                } else {
+                    PatchJump(jzPos, code.Count);
+                }
+                break;
+            default:
+                throw new Exception($"Unhandled stmt {s.GetType().Name}");
         }
     }
 
+    void PatchJump(int pos,int target){ code[pos]=(byte)(target&0xFF); code[pos+1]=(byte)(target>>8); }
+
     void EmitExpr(Expr e){
         switch(e){
             case IntExpr ie:
                 int ci=AddConst(ie.Value); EmitByte(0x01); EmitU16((ushort)ci); break;
             case VarExpr ve:
-                if(!syms.ContainsKey(ve.Name))
-                    throw new Exception($"Unknown variable {ve.Name}");
                 int vi=syms[ve.Name].Index; EmitByte(0x02); EmitU16((ushort)vi); break;
             case BinaryExpr be:
                 EmitExpr(be.L); EmitExpr(be.R);
                 EmitByte(be.Op switch {
                     TokType.PLUS=>0x10, TokType.MINUS=>0x11, TokType.MUL=>0x12, TokType.DIV=>0x13,
-                    _=>throw new Exception("bad op")
+                    TokType.LT=>0x14, TokType.GT=>0x15, TokType.LE=>0x16, TokType.GE=>0x17,
+                    TokType.EQ=>0x18, TokType.NEQ=>0x19,
+                    _=>throw new Exception($"Bad op {be.Op}")
                 });
                 break;
             default: throw new Exception("bad expr");

input.st

@@ -1,9 +1,14 @@
 PROGRAM Demo
 VAR
-  a int16 := 5;
+  a int16 := 3;
-  b byte := a + 3;
+  b int16 := 5;
-  c int32 := b * 2;
+  c int16;
 END_VAR
 
-a := a + c;
+IF a < b THEN
+    c := b - a;
+ELSE
+    c := a - b;
+END_IF;
+
 END_PROGRAM

obj/Debug/net8.0/Compiler.AssemblyInfo.cs

@@ -13,10 +13,10 @@ using System.Reflection;
 [assembly: System.Reflection.AssemblyCompanyAttribute("Compiler")]
 [assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
 [assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
-[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0")]
+[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+0e549b6e0a943de51ec80a7d726000f16f5498dd")]
 [assembly: System.Reflection.AssemblyProductAttribute("Compiler")]
 [assembly: System.Reflection.AssemblyTitleAttribute("Compiler")]
 [assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]
 
-// Generated by the MSBuild WriteCodeFragment class.
+// Von der MSBuild WriteCodeFragment-Klasse generiert.
 

obj/Debug/net8.0/Compiler.AssemblyInfoInputs.cache

@@ -1 +1 @@
-595ce70373ddd00c09969aa302b9639c0cb84849045f0786c137462a6cbd7825
+f8051df38f7774448e56868f6a91a5557659f77e4a8558098bdfd3e3ba758ea4