Adds support for strings

Upsilon/BaseTypes/LuaString.cs

@@ -0,0 +1,76 @@
+using System;
+using Upsilon.BaseTypes.Number;
+
+namespace Upsilon.BaseTypes
+{
+    internal class LuaString : LuaType
+    {
+        public LuaString(string value)
+        {
+            Value = value;
+        }
+
+        public string Value { get; }
+        public override Type Type => Type.String;
+        public override object ToCSharpObject()
+        {
+            return Value;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj == null)
+                return false;
+            if (!(obj is LuaString s))
+                return false;
+            return Equals(s);
+        }
+
+        public override int GetHashCode()
+        {
+            return (Value != null ? Value.GetHashCode() : 0);
+        }
+
+        public bool Equals(LuaString s)
+        {
+            if (s == null) return false;
+            return string.Equals(s.Value, Value);
+        }
+
+        public static LuaString operator +(LuaString a, LuaType b)
+        {
+            switch (b)
+            {
+                case LuaString s:
+                    return a + s;
+                case LuaBoolean bl:
+                    return a + bl;
+                case NumberLong l:
+                    return a + l;
+                case NumberDouble d:
+                    return a + d;
+            }
+            throw new ArgumentException($"Adding Type '{b.Type}' to a LuaString is not supported.");
+        }
+
+        public static LuaString operator +(LuaString a, LuaString b)
+        {
+            return new LuaString(a.Value + b.Value);
+        }
+
+        public static LuaString operator +(LuaString a, LuaBoolean b)
+        {
+            return new LuaString(a.Value + b.Value);
+        }
+
+        public static LuaString operator +(LuaString a, NumberLong b)
+        {
+            return new LuaString(a.Value + b.Value);
+        }
+
+        public static LuaString operator +(LuaString a, NumberDouble b)
+        {
+            return new LuaString(a.Value + b.Value);
+        }
+    }
+}

Upsilon/BaseTypes/LuaType.cs

@@ -1,6 +1,6 @@
 namespace Upsilon.BaseTypes
 {
-    internal abstract class LuaType
+    public abstract class LuaType
     {
         public abstract Type Type { get; }
         public abstract object ToCSharpObject();

Upsilon/Binder/Binder.cs

@@ -129,9 +129,13 @@ namespace Upsilon.Binder
                 case bool b:
                     outValue = new LuaBoolean(b);
                     break;
+                case string s:
+                    outValue = new LuaString(s);
+                    break;
                 case null:
                     outValue = new LuaNull();
                     break;
+
                 default:
                     _diagnostics.LogUnknownType(e.Span);
                     break;

Upsilon/Binder/BoundBinaryOperator.cs

@@ -48,6 +48,15 @@ namespace Upsilon.Binder
             // Boolean equality
             new BoundBinaryOperator(OperatorKind.Equality, Type.Boolean),
             new BoundBinaryOperator(OperatorKind.Inequality, Type.Boolean),
+
+            // String operators
+            new BoundBinaryOperator(OperatorKind.Addition, Type.String, Type.String, Type.String),
+            new BoundBinaryOperator(OperatorKind.Addition, Type.String, Type.Number, Type.String),
+            new BoundBinaryOperator(OperatorKind.Addition, Type.String, Type.Boolean, Type.String),
+
+            // String equality
+            new BoundBinaryOperator(OperatorKind.Equality, Type.String, Type.String, Type.Boolean),
+            new BoundBinaryOperator(OperatorKind.Inequality, Type.String, Type.String, Type.Boolean),
         };
 
         public static BoundBinaryOperator Bind(SyntaxKind operatorToken, Type left, Type right)

Upsilon/Evaluator/Evaluator.cs

@@ -163,7 +163,13 @@ namespace Upsilon.Evaluator
             switch (e.Operator.Kind)
             {
                 case BoundBinaryOperator.OperatorKind.Addition:
-                    return ((Number)left) + ((Number)right);
+                    if (left.Type == Type.Number)
+                        return ((Number)left) + ((Number)right);
+                    else if (left.Type == Type.String)
+                    {
+                        return ((LuaString) left) + right;
+                    }
+                    goto default;
                 case BoundBinaryOperator.OperatorKind.Subtraction:
                     return ((Number)left) - ((Number)right);
                 case BoundBinaryOperator.OperatorKind.Multiplication:

Upsilon/Parser/Lexer.cs

@@ -84,6 +84,8 @@ namespace Upsilon.Parser
                     return new SyntaxToken(SyntaxKind.CloseParenthesis, _position, ")", null);
                 case ',':
                     return new SyntaxToken(SyntaxKind.Comma, _position, ",", null);
+                case '"':
+                    return LexString();
                 case '=':
                     if (Next == '=')
                     {
@@ -135,6 +137,24 @@ namespace Upsilon.Parser
             return new SyntaxToken(SyntaxKind.Number, start, numStr.ToString(), o);
         }
 
+        private SyntaxToken LexString()
+        {
+            var start = _position;
+            var sb = new StringBuilder();
+            while (true)
+            {
+                _position++;
+                if (Current == '"')
+                    break;
+                sb.Append(Current);
+            }
+
+            _position++;
+
+            var res = sb.ToString();
+            return new SyntaxToken(SyntaxKind.String, start, $"\"{res}\"", res);
+        }
+
         private SyntaxToken LexIdentifierOrKeyword()
         {
             var start = _position;

Upsilon/Parser/Parser.cs

@@ -223,6 +223,8 @@ namespace Upsilon.Parser
                 case SyntaxKind.TrueKeyword:
                 case SyntaxKind.FalseKeyword:
                     return ParseBoolean();
+                case SyntaxKind.String:
+                    return ParseString();
                 case SyntaxKind.Identifier:
                     if (Next.Kind == SyntaxKind.OpenParenthesis)
                         return ParseFunctionCallExpression();
@@ -277,5 +279,10 @@ namespace Upsilon.Parser
             return new LiteralExpressionSyntax(token, isTrue);
         }
 
+        private ExpressionSyntax ParseString()
+        {
+            var stringToken = MatchToken(SyntaxKind.String);
+            return new LiteralExpressionSyntax(stringToken, stringToken.Value);
+        }
     }
 }

Upsilon/Parser/SyntaxKind.cs

@@ -20,6 +20,7 @@ namespace Upsilon.Parser
         Tilde,
         TildeEquals,
         Comma,
+        String,
 
         // key words
         TrueKeyword,