Implement While

Parser/Binding/Binder.cs

@@ -132,11 +132,6 @@ namespace Parser.Binding
             };
         }
 
-        private BoundWhileStatement BindWhileStatement(WhileStatementSyntaxNode node)
-        {
-            throw new NotImplementedException();
-        }
-
         private BoundTryCatchStatement BindTryCatchStatement(TryCatchStatementSyntaxNode node)
         {
             throw new NotImplementedException();
@@ -290,6 +285,13 @@ namespace Parser.Binding
             return Identifier(node, ((IdentifierNameExpressionSyntaxNode)node).Name.Text);
         }
 
+        private BoundWhileStatement BindWhileStatement(WhileStatementSyntaxNode node)
+        {
+            var condition = BindConversion(BindExpression(node.Condition), TypeSymbol.Boolean);
+            var body = BindStatement(node.Body);
+            return WhileStatement(node, condition, body);
+        }
+
         private BoundExpressionStatement BindExpressionStatement(ExpressionStatementSyntaxNode node)
         {
             var expression = BindExpression(node.Expression);

Parser/Binding/BoundNodeFactory.cs

@@ -133,6 +133,14 @@ namespace Parser.Binding
             return new BoundGotoStatement(syntax, label);
         }
 
+        public static BoundWhileStatement WhileStatement(
+            SyntaxNode syntax,
+            BoundExpression condition,
+            BoundStatement body)
+        {
+            return new BoundWhileStatement(syntax, condition, body);
+        }
+
         public static BoundIdentifierNameExpression Identifier(
             SyntaxNode syntax,
             string name)

Parser/Binding/BoundRoot.cs

@@ -256,12 +256,18 @@ namespace Parser.Binding
 
     public class BoundWhileStatement : BoundStatement
     {
-        public BoundWhileStatement(SyntaxNode syntax)
+        public BoundWhileStatement(SyntaxNode syntax, BoundExpression condition, BoundStatement body)
             : base(syntax)
         {
+            Condition = condition;
+            Body = body;
         }
 
         public override BoundNodeKind Kind => BoundNodeKind.WhileStatement;
+
+        public BoundExpression Condition { get; }
+
+        public BoundStatement Body { get; }
     }
 
     public abstract class BoundExpression : BoundNode

Parser/Binding/BoundTreeRewriter.cs

@@ -70,7 +70,9 @@ namespace Parser.Binding
 
         public virtual BoundStatement RewriteWhileStatement(BoundWhileStatement node)
         {
-            throw new NotImplementedException();
+            var condition = RewriteExpression(node.Condition);
+            var body = RewriteStatement(node.Body);
+            return WhileStatement(node.Syntax, condition, body);
         }
 
         public virtual BoundStatement RewriteTryCatchStatement(BoundTryCatchStatement node)

Parser/Binding/Conversion.cs

@@ -28,6 +28,11 @@
                 return Implicit;
             }
 
+            if (to == TypeSymbol.Boolean)
+            {
+                return Implicit;
+            }
+
             return None;
         }
     }

Parser/Emitting/Emitter.cs

@@ -467,8 +467,13 @@ namespace Parser.Emitting
 
         private void EmitConditionalGoto(BoundConditionalGotoStatement node, ILProcessor ilProcessor)
         {
-            EmitExpression(node.Condition, ilProcessor);
+            var condition = ConvertExpression(node.Condition, TypeSymbol.Boolean);
-            ilProcessor.Emit(OpCodes.Call, _mObjectToBool);
+            if (condition is null)
+            {
+                throw new Exception("Cannot cast a condition in GOTO to boolean.");
+            }
+
+            EmitExpression(condition, ilProcessor);
             var instruction = node.GotoIfTrue ? OpCodes.Brtrue : OpCodes.Brfalse;
             if (_labels.TryGetValue(node.Label, out var target))
             {
@@ -569,7 +574,7 @@ namespace Parser.Emitting
             {
                 ilProcessor.Emit(OpCodes.Call, _doubleToMObject);
             }
-            if ((fromType, toType) == (TypeSymbol.Int, TypeSymbol.MObject))
+            else if ((fromType, toType) == (TypeSymbol.Int, TypeSymbol.MObject))
             {
                 ilProcessor.Emit(OpCodes.Call, _intToMObject);
             }
@@ -577,6 +582,10 @@ namespace Parser.Emitting
             {
                 ilProcessor.Emit(OpCodes.Call, _stringToMObject);
             }
+            else if ((fromType, toType) == (TypeSymbol.MObject, TypeSymbol.Boolean))
+            {
+                ilProcessor.Emit(OpCodes.Call, _mObjectToBool);
+            }
             else
             {
                 throw new NotImplementedException($"Conversion of '{fromType}' to '{toType}' is not implemented.");

Parser/Lowering/Lowerer.cs

@@ -86,6 +86,41 @@ namespace Parser.Lowering
             return RewriteBlockStatement(Block(node.Syntax, builder.ToArray()));
         }
 
+        public override BoundStatement RewriteWhileStatement(BoundWhileStatement node)
+        {
+            // while cond
+            //     body
+            // end
+            //
+            //      |
+            //      |
+            //      V
+            //
+            // LabelLoop:
+            //     gotoFalse cond LabelEnd
+            //     body
+            //     goto LabelLoop
+            // LabelEnd:
+            var labelLoop = GenerateLabel();
+            var labelEnd = GenerateLabel();
+            var result = Block(
+                node.Syntax,
+                // LabelLoop:
+                LabelStatement(node.Syntax, labelLoop),
+                //     gotoFalse cond LabelEnd
+                GotoIfFalse(
+                    node.Syntax,
+                    node.Condition,
+                    labelEnd),
+                //     body
+                node.Body,
+                //     goto LabelLoop
+                Goto(node.Syntax, labelLoop),
+                // LabelEnd:
+                LabelStatement(node.Syntax, labelEnd));
+            return RewriteBlockStatement(result);
+        }
+
         public override BoundStatement RewriteForStatement(BoundForStatement node)
         {
             // for i = expr
@@ -102,7 +137,6 @@ namespace Parser.Lowering
             //   #index = #index + 1
             //   goto LabelLoop
             // LabelEnd:
-            var builder = ImmutableArray.CreateBuilder<BoundStatement>();
             var labelLoop = GenerateLabel();
             var labelEnd = GenerateLabel();
             var localArray = GenerateTypedLocalVariable(TypeSymbol.MObject);

examples/helloworld/hello.m

@@ -5,6 +5,12 @@ f(x);
 x = 3;
 f(x);
 
+i = 1;
+while i <= 10
+    disp(i);
+    i = i + 1;
+end
+
 % for i = 1:10
 %     disp(i);
 % end