Cleaning up tokenizer

Author: miroiu

StringMath/Tokenizer/ITokenizer.cs

@@ -0,0 +1,10 @@
+namespace StringMath
+{
+    /// <summary>Contract for tokenizers.</summary>
+    internal interface ITokenizer
+    {
+        /// <summary>Reads the next token in the token stream.</summary>
+        /// <returns>A token.</returns>
+        Token ReadToken();
+    }
+}

StringMath/Tokenizer/Token.cs

@@ -1,11 +1,29 @@
 namespace StringMath
 {
-    internal struct Token
+    /// <summary>A token containing basic information about some text.</summary>
+    internal readonly struct Token
     {
-        public int Position;
-        public string Text;
-        public TokenType Type;
+        /// <summary>Initializes a new instance of a token.</summary>
+        /// <param name="type">The token type.</param>
+        /// <param name="text">The token value.</param>
+        /// <param name="position">The token's position in the input string.</param>
+        public Token(TokenType type, string text, int position)
+        {
+            Type = type;
+            Text = text;
+            Position = position;
+        }
+
+        /// <summary>The token's position in the input string.</summary>
+        public readonly int Position;
+
+        /// <summary>The token value.</summary>
+        public readonly string Text;
+
+        /// <summary>The token type.</summary>
+        public readonly TokenType Type;
 
+        /// <inheritdoc />
         public override string ToString()
         {
             return $"{Text} ({Type}):{Position}";

StringMath/Tokenizer/TokenType.cs

@@ -3,6 +3,9 @@
     /// <summary>Available token types.</summary>
     internal enum TokenType
     {
+        /// <summary>Unknown token.</summary>
+        Unknown,
+
         /// <summary>\0</summary>
         EndOfCode,
 

StringMath/Tokenizer/Tokenizer.Helpers.cs

@@ -18,11 +18,8 @@ private string ReadIdentifier(ISourceText stream)
             }
             else
             {
-                throw LangException.UnexpectedToken(new Token
-                {
-                    Position = stream.Position,
-                    Text = stream.Current.ToString()
-                }, TokenType.Identifier);
+                Token token = new Token(TokenType.Unknown, stream.Current.ToString(), stream.Position);
+                throw LangException.UnexpectedToken(token, TokenType.Identifier);
             }
 
             while (stream.Current != identifierTerminator)
@@ -34,23 +31,22 @@ private string ReadIdentifier(ISourceText stream)
                 }
                 else
                 {
-                    throw LangException.UnexpectedToken(new Token
-                    {
-                        Position = stream.Position,
-                        Text = stream.Current.ToString()
-                    }, identifierTerminator);
+                    Token token = new Token(TokenType.Unknown, stream.Current.ToString(), stream.Position);
+                    throw LangException.UnexpectedToken(token, identifierTerminator);
                 }
             }
 
             builder.Append(stream.Current);
             stream.MoveNext();
             string text = builder.ToString();
 
-            return text.Length == 2 ? throw LangException.UnexpectedToken(new Token
+            if (text.Length == 2)
             {
-                Position = stream.Position - 1,
-                Text = identifierTerminator.ToString()
-            }, identifierTerminator) : text;
+                Token token = new Token(TokenType.Unknown, identifierTerminator.ToString(), stream.Position - 1);
+                throw LangException.UnexpectedToken(token, identifierTerminator);
+            }
+
+            return text;
         }
 
         private string ReadOperator(ISourceText stream)
@@ -84,11 +80,8 @@ private string ReadNumber(ISourceText stream)
                     }
                     else
                     {
-                        throw LangException.UnexpectedToken(new Token
-                        {
-                            Position = stream.Position,
-                            Text = stream.Current.ToString()
-                        }, TokenType.Number);
+                        Token token = new Token(TokenType.Unknown, stream.Current.ToString(), stream.Position);
+                        throw LangException.UnexpectedToken(token, TokenType.Number);
                     }
                 }
                 else if (char.IsDigit(stream.Current))
@@ -103,11 +96,14 @@ private string ReadNumber(ISourceText stream)
             }
 
             char peeked = stream.Peek(-1);
-            return peeked == '.' ? throw LangException.UnexpectedToken(new Token
+
+            if (peeked == '.')
             {
-                Position = stream.Position,
-                Text = peeked.ToString()
-            }, TokenType.Number) : builder.ToString();
+                Token token = new Token(TokenType.Unknown, peeked.ToString(), stream.Position);
+                throw LangException.UnexpectedToken(token, TokenType.Number);
+            }
+
+            return builder.ToString();
         }
 
         private void ReadWhiteSpace(ISourceText stream)

StringMath/Tokenizer/Tokenizer.cs

@@ -2,14 +2,6 @@
 
 namespace StringMath
 {
-    /// <summary>Contract for tokenizers.</summary>
-    internal interface ITokenizer
-    {
-        /// <summary>Reads the next token in the token stream.</summary>
-        /// <returns>A token.</returns>
-        Token ReadToken();
-    }
-
     /// <inheritdoc />
     internal sealed partial class Tokenizer : ITokenizer
     {
@@ -27,7 +19,7 @@ public Tokenizer(ISourceText text)
         {
             _text = text;
         }
-        
+
         /// <summary>Creates a new instance of the tokenizer.</summary>
         /// <param name="text">The text to tokenize.</param>
         public Tokenizer(string text) : this(new SourceText(text))
@@ -37,12 +29,6 @@ public Tokenizer(string text) : this(new SourceText(text))
         /// <inheritdoc />
         public Token ReadToken()
         {
-            Token token = new Token
-            {
-                Text = $"{_text.Current}",
-                Position = _text.Position
-            };
-
             switch (_text.Current)
             {
                 case '.':
@@ -56,29 +42,22 @@ public Token ReadToken()
                 case '7':
                 case '8':
                 case '9':
-                    token.Type = TokenType.Number;
-                    token.Text = ReadNumber(_text);
-                    break;
+                    return new Token(TokenType.Number, ReadNumber(_text), _text.Position);
 
                 case '(':
-                    token.Type = TokenType.OpenParen;
                     _text.MoveNext();
-                    break;
+                    return new Token(TokenType.OpenParen, "(", _text.Position);
 
                 case ')':
-                    token.Type = TokenType.CloseParen;
                     _text.MoveNext();
-                    break;
+                    return new Token(TokenType.CloseParen, ")", _text.Position);
 
                 case '{':
-                    token.Type = TokenType.Identifier;
-                    token.Text = ReadIdentifier(_text);
-                    break;
+                    return new Token(TokenType.Identifier, ReadIdentifier(_text), _text.Position);
 
                 case '!':
-                    token.Type = TokenType.Exclamation;
                     _text.MoveNext();
-                    break;
+                    return new Token(TokenType.Exclamation, "!", _text.Position);
 
                 case ' ':
                 case '\t':
@@ -91,17 +70,12 @@ public Token ReadToken()
                     return ReadToken();
 
                 case '\0':
-                    token.Type = TokenType.EndOfCode;
-                    break;
+                    return new Token(TokenType.EndOfCode, "\0", _text.Position);
 
                 default:
                     string op = ReadOperator(_text);
-                    token.Text = op;
-                    token.Type = TokenType.Operator;
-                    break;
+                    return new Token(TokenType.Operator, op, _text.Position);
             }
-
-            return token;
         }
 
         /// <inheritdoc />