handle then branch better

chrisjbreisch · May 22, 2022 · a40c9b3 · a40c9b3
1 parent 8d435eb
commit a40c9b3
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Showing 7 changed files with 93 additions and 34 deletions.
diff --git a/Trs80.Level1Basic.Interpreter.Test/InterpreterTest.cs b/Trs80.Level1Basic.Interpreter.Test/InterpreterTest.cs
@@ -934,4 +934,44 @@ public void Interpreter_Evaluates_Logical_Expressions8()
         controller.ReadOutputLine().Should().Be("FALSE");
         controller.IsEndOfRun().Should().BeTrue();
     }
+
+    [TestMethod]
+    public void Interpreter_Executes_Return_After_Then()
+    {
+        using var controller = new TestController();
+        var program = new List<string> {
+            "10 a=0",
+            "20 gosub 100",
+            "30 print \"SUCCESS!\"",
+            "40 end",
+            "100 if a = 0 then return",
+            "110 print \"FAIL!\"",
+            "120 end"
+        };
+
+        controller.RunProgram(program);
+
+        controller.ReadOutputLine().Should().Be("SUCCESS!");
+        controller.IsEndOfRun().Should().BeTrue();
+    }
+
+    [TestMethod]
+    public void Interpreter_Executes_Goto_After_Multiple_Thens()
+    {
+        using var controller = new TestController();
+        var program = new List<string> {
+            "10 a=0",
+            "20 if a = 0 then a = 1 : goto 100",
+            "30 print a",
+            "40 end",
+            "100 a = 2",
+            "110 print a",
+            "120 end"
+        };
+
+        controller.RunProgram(program);
+
+        controller.ReadOutputLine().Should().Be(" 2 ");
+        controller.IsEndOfRun().Should().BeTrue();
+    }
 }
diff --git a/Trs80.Level1Basic.VirtualMachine/Exceptions/ReturnFromGosub.cs b/Trs80.Level1Basic.VirtualMachine/Exceptions/ReturnFromGosub.cs
@@ -0,0 +1,8 @@
+
+using System;
+
+namespace Trs80.Level1Basic.VirtualMachine.Exceptions;
+
+public class ReturnFromGosub : Exception
+{
+}
diff --git a/Trs80.Level1Basic.VirtualMachine/Interpreter/Interpreter.cs b/Trs80.Level1Basic.VirtualMachine/Interpreter/Interpreter.cs
@@ -2,7 +2,7 @@
 using System.Linq;
 using System.Text;
 using System.Threading;
-
+using Microsoft.CSharp.RuntimeBinder;
 using Trs80.Level1Basic.HostMachine;
 using Trs80.Level1Basic.VirtualMachine.Exceptions;
 using Trs80.Level1Basic.VirtualMachine.Machine;
@@ -233,6 +233,10 @@ public void Execute(IStatement statement)
         {
             statement.Accept(this);
         }
+        catch (ReturnFromGosub)
+        {
+            throw;
+        }
         catch (ScanException)
         {
             throw;
@@ -334,12 +338,10 @@ public Void VisitForStatement(For statement)
 
     public Void VisitGosubStatement(Gosub statement)
     {
-        IStatement nextStatement = _machine.GetNextStatement(_program.CurrentStatement);
+        IStatement resumeStatement = _machine.GetNextStatement(_program.CurrentStatement);
 
         IStatement jumpToStatement = GetJumpToStatement(statement, statement.Location, "GOSUB");
-        _machine.RunStatementList(jumpToStatement, this, false);
-
-        _machine.SetNextStatement(nextStatement);
+        ExecuteGosub(jumpToStatement, resumeStatement);
 
         return null!;
     }
@@ -365,40 +367,19 @@ private IStatement GetStatementByLineNumber(int lineNumber)
     public Void VisitGotoStatement(Goto statement)
     {
         IStatement jumpToStatement = GetJumpToStatement(statement, statement.Location, "GOTO");
-        _machine.RunStatementList(jumpToStatement, this, false);
-        _machine.ExecutionHalted = true;
-
+        _machine.SetNextStatement(jumpToStatement);
         return null!;
     }
 
     public Void VisitIfStatement(If statement)
     {
         if (!IsTruthy(Evaluate(statement.Condition))) return null!;
 
-        IStatement thenStatement = statement.ThenBranch?[0];
-        if (thenStatement == null) return null!;
+        _machine.RunThenBranch(statement.ThenBranch, this);
 
-        switch (thenStatement)
-        {
-            case Goto gotoStatement:
-                VisitGotoStatement(gotoStatement);
-                break;
-            default:
-                ExecuteThenBranch(statement.ThenBranch);
-                break;
-        }
         return null!;
     }
 
-    private void ExecuteThenBranch(CompoundStatementList thenBranch)
-    {
-        IStatement nextStatement = _machine.GetNextStatement(_program.CurrentStatement);
-
-        _machine.RunStatementList(thenBranch[0], this, true);
-
-        _machine.SetNextStatement(nextStatement);
-    }
-
     public Void VisitInputStatement(Input statement)
     {
         foreach (Expression expression in statement.Expressions)
@@ -594,8 +575,7 @@ public Void VisitOnStatement(On statement)
             IStatement resumeStatement = _machine.GetNextStatement(statement);
             Expression location = new Literal(locations[selector]);
             IStatement jumpToStatement = GetJumpToStatement(statement, location, "GOSUB");
-            _machine.RunStatementList(jumpToStatement, this, false);
-            _machine.SetNextStatement(resumeStatement);
+            ExecuteGosub(jumpToStatement, resumeStatement);
 
             return null!;
         }
@@ -611,6 +591,18 @@ public Void VisitOnStatement(On statement)
         return null!;
     }
 
+    private void ExecuteGosub(IStatement jumpToStatement, IStatement resumeStatement)
+    {
+        try
+        {
+            _machine.RunStatementList(jumpToStatement, this, false);
+        }
+        catch (ReturnFromGosub)
+        {
+            _machine.SetNextStatement(resumeStatement);
+        }
+    }
+
     public Void VisitPrintStatement(Print statement)
     {
         if (statement.AtPosition != null) PrintAt(statement.AtPosition);
@@ -674,9 +666,7 @@ public Void VisitRestoreStatement(Restore _)
 
     public Void VisitReturnStatement(Return statement)
     {
-        _machine.SetNextStatement(null);
-
-        return null!;
+        throw new ReturnFromGosub();
     }
 
     public Void VisitRunStatement(Run statement)

diff --git a/Trs80.Level1Basic.VirtualMachine/Machine/IMachine.cs b/Trs80.Level1Basic.VirtualMachine/Machine/IMachine.cs
@@ -26,6 +26,7 @@ public interface IMachine
     void LoadProgram(string path);
     void NewProgram();
     void RunStatementList(IStatement statement, IInterpreter interpreter, bool breakOnLineChange);
+    void RunThenBranch(CompoundStatementList thenBranch, IInterpreter interpreter);
     void SetNextStatement(IStatement statement);
     void HaltRun();
     IStatement GetStatementByLineNumber(int lineNumber);

diff --git a/Trs80.Level1Basic.VirtualMachine/Machine/Machine.cs b/Trs80.Level1Basic.VirtualMachine/Machine/Machine.cs
@@ -139,6 +139,25 @@ public void RunStatementList(IStatement statement, IInterpreter interpreter, boo
         }
     }
 
+    public void RunThenBranch(CompoundStatementList thenBranch, IInterpreter interpreter)
+    {
+        IStatement nextStatement = _nextStatement;
+
+        ExecutionHalted = false;
+        if (thenBranch == null) return;
+        int lineNumber = thenBranch.LineNumber;
+        IStatement statement = thenBranch[0];
+
+        while (statement != null && !ExecutionHalted)
+        {
+            _nextStatement = GetNextStatement(statement);
+            interpreter.Execute(statement);
+            if (statement is IListStatementDecorator decorated && decorated.BaseType() == typeof(Goto)) return;
+            statement = _nextStatement;
+        }
+        SetNextStatement(nextStatement);
+    }
+
     public IStatement GetStatementByLineNumber(int lineNumber)
     {
         return Program.GetExecutableStatement(lineNumber);

diff --git a/Trs80.Level1Basic.sln.DotSettings b/Trs80.Level1Basic.sln.DotSettings
@@ -1,5 +1,6 @@
 <wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=builtins/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=gosub/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=hellogoodbye/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=hwnd/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Lucida/@EntryIndexedValue">True</s:Boolean>

diff --git a/Trs80.Level1Basic/Samples/ParserTests/recursiveFib.bas b/Trs80.Level1Basic/Samples/ParserTests/recursiveFib.bas
@@ -9,5 +9,5 @@
 1030 gosub 1010
 1040 n = n + 1
 1050 a(n) = a(n-1) + a(n-2)
-1060 rem runprint "#1060 n=";n;"a(";n;")=";a(n);"a(";n-1;")=";a(n-1);"a(";n-2;")=";a(n-2)
+1060 rem print "#1060 n=";n;"a(";n;")=";a(n);"a(";n-1;")=";a(n-1);"a(";n-2;")=";a(n-2)
 1070 return