Implement function calls

Parser/Binding/Binder.cs

@@ -18,23 +18,24 @@ namespace Parser.Binding
             var binder = new Binder();
             var boundRoot = binder.BindRoot(syntaxTree.NullRoot);
             var statements = ((BoundBlockStatement)boundRoot.File.Body).Statements;
-            var functionsBuilder = ImmutableDictionary.CreateBuilder<FunctionSymbol, BoundBlockStatement>();
+            var functionsBuilder = ImmutableDictionary.CreateBuilder<FunctionSymbol, LoweredFunction>();
             var globalStatements = statements.Where(s => s.Kind != BoundNodeKind.FunctionDeclaration).ToArray();
             var mainFunction = (FunctionSymbol?)null;
             var scriptFunction = (FunctionSymbol?)null;
             if (globalStatements.Length > 0)
             {
                 // we have to gather all bound expression statements into a "script" function.
-                scriptFunction = new FunctionSymbol(
+                scriptFunction = new FunctionSymbol("%script");
-                    name: "%script",
-                    parameters: ImmutableArray<ParameterSymbol>.Empty,
-                    declaration: null);
                 var body = Block(globalStatements[0].Syntax, globalStatements);
                 var loweredBody = Lowerer.Lower(body);
-                functionsBuilder.Add(scriptFunction, loweredBody);
+                var declaration = new BoundFunctionDeclaration(
-            }
+                    syntax: globalStatements[0].Syntax,
-            else
+                    name: "%script",
-            {
+                    inputDescription: ImmutableArray<ParameterSymbol>.Empty,
+                    outputDescription: ImmutableArray<ParameterSymbol>.Empty,
+                    body: body);
+                var loweredFunction = LowerFunction(declaration);
+                functionsBuilder.Add(scriptFunction, loweredFunction);
             }
 
             var functions = statements.OfType<BoundFunctionDeclaration>().ToArray();
@@ -42,11 +43,9 @@ namespace Parser.Binding
             foreach (var function in functions)
             {
                 var functionSymbol = new FunctionSymbol(
-                    name: function.Name,
+                    name: function.Name);
-                    parameters: function.InputDescription,
+                var loweredFunction = LowerFunction(function);
-                    declaration: (FunctionDeclarationSyntaxNode)function.Syntax);
+                functionsBuilder.Add(functionSymbol, loweredFunction);
-                var loweredBody = Lowerer.Lower(function.Body);
-                functionsBuilder.Add(functionSymbol, loweredBody);
                 if (first && globalStatements.Length == 0)
                 {
                     // the first function in a file will become "main".
@@ -62,6 +61,17 @@ namespace Parser.Binding
                 functionsBuilder.ToImmutable());
         }
 
+        private static LoweredFunction LowerFunction(BoundFunctionDeclaration declaration)
+        {
+            var loweredBody = Lowerer.Lower(declaration.Body);
+            return new LoweredFunction(
+                declaration: declaration,
+                name: declaration.Name,
+                inputDescription: declaration.InputDescription,
+                outputDescription: declaration.OutputDescription,
+                body: loweredBody);
+        }
+
         private BoundRoot BindRoot(RootSyntaxNode node)
         {
             var boundFile = BindFile(node.File);

Parser/Binding/BoundProgram.cs

@@ -9,7 +9,7 @@ namespace Parser.Binding
             ImmutableArray<Diagnostic> diagnostics,
             FunctionSymbol? mainFunction,
             FunctionSymbol? scriptFunction,
-            ImmutableDictionary<FunctionSymbol, BoundBlockStatement> functions)
+            ImmutableDictionary<FunctionSymbol, LoweredFunction> functions)
         {
             Diagnostics = diagnostics;
             MainFunction = mainFunction;
@@ -32,6 +32,6 @@ namespace Parser.Binding
         /// <summary>
         /// So-called "local" functions.
         /// </summary>
-        public ImmutableDictionary<FunctionSymbol, BoundBlockStatement> Functions { get; }
+        public ImmutableDictionary<FunctionSymbol, LoweredFunction> Functions { get; }
     }
 }

Parser/Binding/BoundRoot.cs

@@ -156,6 +156,21 @@ namespace Parser.Binding
         public ImmutableArray<ParameterSymbol> InputDescription { get; }
         public ImmutableArray<ParameterSymbol> OutputDescription { get; }
         public BoundStatement Body { get; }
+
+        public BoundFunctionDeclaration WithBody(BoundStatement body)
+        {
+            if (body == Body)
+            {
+                return this;
+            }
+
+            return new BoundFunctionDeclaration(
+                Syntax,
+                Name,
+                InputDescription,
+                OutputDescription,
+                body);
+        }
     }
 
     public class BoundGotoStatement : BoundStatement

Parser/Binding/FunctionSymbol.cs

@@ -1,23 +1,13 @@
-using System.Collections.Immutable;
+namespace Parser.Binding
-
-namespace Parser.Binding
 {
     public class FunctionSymbol
     {
         public FunctionSymbol(
-            string name,
+            string name)
-            ImmutableArray<ParameterSymbol> parameters,
-            FunctionDeclarationSyntaxNode? declaration)
         {
             Name = name;
-            Parameters = parameters;
-            Declaration = declaration;
         }
 
         public string Name { get; }
-
-        public ImmutableArray<ParameterSymbol> Parameters { get; }
-
-        public FunctionDeclarationSyntaxNode? Declaration { get; }
     }
 }

Parser/Binding/LoweredFunction.cs

@@ -0,0 +1,26 @@
+using System.Collections.Immutable;
+
+namespace Parser.Binding
+{
+    public class LoweredFunction {
+        public LoweredFunction(
+            BoundFunctionDeclaration declaration,
+            string name,
+            ImmutableArray<ParameterSymbol> inputDescription,
+            ImmutableArray<ParameterSymbol> outputDescription,
+            BoundBlockStatement body)
+        {
+            Declaration = declaration;
+            Name = name;
+            InputDescription = inputDescription;
+            OutputDescription = outputDescription;
+            Body = body;
+        }
+
+        public BoundFunctionDeclaration Declaration { get; }
+        public string Name { get; }
+        public ImmutableArray<ParameterSymbol> InputDescription { get; }
+        public ImmutableArray<ParameterSymbol> OutputDescription { get; }
+        public BoundBlockStatement Body { get; }
+    }
+}

Parser/Evaluator.cs

@@ -5,6 +5,7 @@ using Parser.Objects;
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Linq;
 
 namespace Parser
 {
@@ -15,6 +16,7 @@ namespace Parser
         private readonly DiagnosticsBag _diagnostics = new DiagnosticsBag();
         private bool _inRepl = false;
         private readonly Stack<EvaluationScope> _scopeStack = new Stack<EvaluationScope>();
+        private readonly Dictionary<FunctionSymbol, LoweredFunction> _functions = new Dictionary<FunctionSymbol, LoweredFunction>();
 
         public Evaluator(BoundProgram program, CompilationContext context, bool inRepl)
         {
@@ -23,28 +25,34 @@ namespace Parser
             var outerScope = new EvaluationScope();
             _scopeStack.Push(outerScope);
             _inRepl = inRepl;
+            foreach (var pair in program.Functions)
+            {
+                _functions[pair.Key] = pair.Value;
+            }
         }
 
         internal EvaluationResult Evaluate()
         {
-            if (_program.MainFunction is { } mainFunction)
+            if (_program.MainFunction is { } mainFunctionSymbol)
             {
-                if (mainFunction.Parameters.Length > 0)
+                var mainFunction = _program.Functions[mainFunctionSymbol];
+                if (mainFunction.InputDescription.Length > 0)
                 {
                     _diagnostics.ReportNotEnoughInputs(
-                        new TextSpan(mainFunction.Declaration.Position, mainFunction.Declaration.Position + mainFunction.Declaration.FullWidth),
+                        new TextSpan(mainFunction.Body.Syntax.Position, mainFunction.Body.Syntax.Position + mainFunction.Body.Syntax.FullWidth),
                         mainFunction.Name);
                 return new EvaluationResult(null, _diagnostics.ToImmutableArray());
                 }
                 else
                 {
-                    var result = EvaluateBlockStatement(_program.Functions[mainFunction]);
+                    var result = EvaluateBlockStatement(mainFunction.Body);
                     return new EvaluationResult(result, _diagnostics.ToImmutableArray());
                 }
             }
-            else if (_program.ScriptFunction is { } scriptFunction)
+            else if (_program.ScriptFunction is { } scriptFunctionSymbol)
             {
-                var result = EvaluateBlockStatement(_program.Functions[scriptFunction]);
+                var scriptFunction = _program.Functions[scriptFunctionSymbol];
+                var result = EvaluateBlockStatement(scriptFunction.Body);
                 return new EvaluationResult(result, _diagnostics.ToImmutableArray());
             }
             else
@@ -304,10 +312,58 @@ namespace Parser
             }
             else
             {
-                throw new NotImplementedException("Functions are not supported.");
+                var resolvedFunction = ResolveFunction(function);
+                if (resolvedFunction is null)
+                {
+                    _diagnostics.ReportFunctionNotFound(
+                        new TextSpan(
+                            node.Name.Syntax.Position,
+                            node.Name.Syntax.Position + node.Name.Syntax.FullWidth),
+                        function.Name);
+                    return null;
+                }
+                else
+                {
+                    // bring arguments into context
+                    var newScope = new EvaluationScope();
+                    var counter = 0;
+                    foreach (var expectedArgument in resolvedFunction.InputDescription)
+                    {
+                        if (counter >= arguments.Count)
+                        {
+                            break;
+                        }
+                        newScope.Variables.Add(expectedArgument.Name, arguments[counter]);
+                        counter++;
+                    }
+
+                    if (counter < arguments.Count)
+                    {
+                        _diagnostics.ReportTooManyInputs(
+                            new TextSpan(
+                                node.Arguments[counter].Syntax.Position,
+                                node.Arguments[counter].Syntax.Position + node.Arguments[counter].Syntax.FullWidth),
+                        function.Name);
+                        return null;
+                    }
+                    _scopeStack.Push(newScope);
+                    var result = EvaluateBlockStatement(resolvedFunction.Body);
+                    _scopeStack.Pop();
+                    return result;
+                }
             }
         }
 
+        private LoweredFunction? ResolveFunction(UnresolvedFunctionSymbol functionSymbol)
+        {
+            var maybeKey = _functions.Keys.FirstOrDefault(k => k.Name == functionSymbol.Name);
+            return maybeKey switch
+            {
+                { } key => _functions[key],
+                _ => null,
+            };
+        }
+
         private MObject? EvaluateDisp(List<MObject> arguments)
         {
             if (arguments.Count != 1)
@@ -319,11 +375,11 @@ namespace Parser
             return arguments[0];
         }
 
-        private FunctionSymbol GetFunctionSymbol(BoundExpression functionName)
+        private UnresolvedFunctionSymbol GetFunctionSymbol(BoundExpression functionName)
         {
             if (functionName.Kind == BoundNodeKind.IdentifierNameExpression)
             {
-                return new FunctionSymbol(((BoundIdentifierNameExpression)functionName).Name);
+                return new UnresolvedFunctionSymbol(((BoundIdentifierNameExpression)functionName).Name);
             }
 
             throw new NotImplementedException($"Unknown function symbol '{functionName.Syntax.Text}'.");

Parser/Internal/DiagnosticsBag.cs

@@ -92,5 +92,15 @@ namespace Parser.Internal
         {
             Report(span, $"Variable '{variableName}' not found.");
         }
+
+        internal void ReportFunctionNotFound(TextSpan span, string functionName)
+        {
+            Report(span, $"Function '{functionName}' not found.");
+        }
+
+        internal void ReportTooManyInputs(TextSpan span, string functionName)
+        {
+            Report(span, $"Too many inputs in the call to '{functionName}'.");
+        }
     }
 }

Parser/UnresolvedFunctionSymbol.cs

@@ -1,10 +1,10 @@
 namespace Parser
 {
-    internal class FunctionSymbol
+    internal class UnresolvedFunctionSymbol
     {
         public string Name { get; }
 
-        public FunctionSymbol(string name)
+        public UnresolvedFunctionSymbol(string name)
         {
             Name = name;
         }

examples/helloworld/hello.m

@@ -1,13 +1,11 @@
 x = 2;
-y = 3;
+f(x);
-disp(x + y * y);
+f(x);
-disp('Hello world!');
 
-x = 2 * 3;
+function f(x)
-if x > 5
+    disp('X was');
-    y = 'Greater than 5';
+    disp(x);
-elseif x > 0
+    x = x + 1;
-    y = 10;
+    disp('X is')
-end
+    disp(x);
-
+end
-disp(y);