Initial Commit

src/main/kotlin/gay/pizza/pork/PorkLanguage.kt

@@ -0,0 +1,3 @@
+package gay.pizza.pork
+
+object PorkLanguage

src/main/kotlin/gay/pizza/pork/ast/BooleanLiteral.kt

@@ -0,0 +1,5 @@
+package gay.pizza.pork.ast
+
+class BooleanLiteral(val value: Boolean) : Expression {
+  override val type: NodeType = NodeType.BooleanLiteral
+}

src/main/kotlin/gay/pizza/pork/ast/Define.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+class Define(val symbol: Symbol, val value: Expression) : Expression {
+  override val type: NodeType = NodeType.Define
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    listOf(visitor.visit(symbol), visitor.visit(value))
+}

src/main/kotlin/gay/pizza/pork/ast/Expression.kt

@@ -0,0 +1,3 @@
+package gay.pizza.pork.ast
+
+interface Expression : Node

src/main/kotlin/gay/pizza/pork/ast/FunctionCall.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+class FunctionCall(val symbol: Symbol) : Expression {
+  override val type: NodeType = NodeType.FunctionCall
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    listOf(visitor.visit(symbol))
+}

src/main/kotlin/gay/pizza/pork/ast/InfixOperation.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+class InfixOperation(val left: Expression, val op: InfixOperator, val right: Expression) : Expression {
+  override val type: NodeType = NodeType.InfixOperation
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    listOf(visitor.visit(left), visitor.visit(right))
+}

src/main/kotlin/gay/pizza/pork/ast/InfixOperator.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+enum class InfixOperator(val token: String) {
+  Plus("+"),
+  Minus("-"),
+  Multiply("*"),
+  Divide("/")
+}

src/main/kotlin/gay/pizza/pork/ast/IntLiteral.kt

@@ -0,0 +1,5 @@
+package gay.pizza.pork.ast
+
+class IntLiteral(val value: Int) : Expression {
+  override val type: NodeType = NodeType.IntLiteral
+}

src/main/kotlin/gay/pizza/pork/ast/Lambda.kt

@@ -0,0 +1,10 @@
+package gay.pizza.pork.ast
+
+class Lambda(val expressions: List<Expression>) : Expression {
+  constructor(vararg expressions: Expression) : this(listOf(*expressions))
+
+  override val type: NodeType = NodeType.Lambda
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    expressions.map { expression ->  visitor.visit(expression) }
+}

src/main/kotlin/gay/pizza/pork/ast/ListLiteral.kt

@@ -0,0 +1,10 @@
+package gay.pizza.pork.ast
+
+class ListLiteral(val items: List<Expression>) : Expression {
+  constructor(vararg items: Expression) : this(listOf(*items))
+
+  override val type: NodeType = NodeType.ListLiteral
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    items.map { visitor.visit(it) }
+}

src/main/kotlin/gay/pizza/pork/ast/Node.kt

@@ -0,0 +1,6 @@
+package gay.pizza.pork.ast
+
+interface Node {
+  val type: NodeType
+  fun <T> visitChildren(visitor: Visitor<T>): List<T> = emptyList()
+}

src/main/kotlin/gay/pizza/pork/ast/NodeType.kt

@@ -0,0 +1,37 @@
+package gay.pizza.pork.ast
+
+import gay.pizza.pork.ast.NodeTypeTrait.*
+
+enum class NodeType(val parent: NodeType? = null, vararg traits: NodeTypeTrait) {
+  Node,
+  Symbol(Node),
+  Expression(Node, Intermediate),
+  Program(Node),
+  IntLiteral(Expression, Literal),
+  BooleanLiteral(Expression, Literal),
+  ListLiteral(Expression, Literal),
+  Parentheses(Expression),
+  Define(Expression),
+  Lambda(Expression),
+  InfixOperation(Expression),
+  SymbolReference(Expression),
+  FunctionCall(Expression);
+
+  val parents: Set<NodeType>
+
+  init {
+    val calculatedParents = mutableListOf<NodeType>()
+    var self = this
+    while (true) {
+      calculatedParents.add(self)
+      if (self.parent != null) {
+        self = self.parent!!
+      } else {
+        break
+      }
+    }
+    parents = calculatedParents.toSet()
+  }
+
+  fun isa(type: NodeType): Boolean = this == type || parents.contains(type)
+}

src/main/kotlin/gay/pizza/pork/ast/NodeTypeTrait.kt

@@ -0,0 +1,6 @@
+package gay.pizza.pork.ast
+
+enum class NodeTypeTrait {
+  Intermediate,
+  Literal
+}

src/main/kotlin/gay/pizza/pork/ast/Parentheses.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+class Parentheses(val expression: Expression) : Expression {
+  override val type: NodeType = NodeType.Parentheses
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    listOf(visitor.visit(expression))
+}

src/main/kotlin/gay/pizza/pork/ast/Printer.kt

@@ -0,0 +1,100 @@
+package gay.pizza.pork.ast
+
+class Printer(private val buffer: StringBuilder) : Visitor<Unit> {
+  private var indent = 0
+
+  private fun append(text: String) {
+    buffer.append(text)
+  }
+
+  private fun appendLine() {
+    buffer.appendLine()
+  }
+
+  private fun indent() {
+    repeat(indent) {
+      append("  ")
+    }
+  }
+
+  override fun visitDefine(node: Define) {
+    visit(node.symbol)
+    append(" = ")
+    visit(node.value)
+  }
+
+  override fun visitFunctionCall(node: FunctionCall) {
+    visit(node.symbol)
+    append("()")
+  }
+
+  override fun visitReference(node: SymbolReference) {
+    visit(node.symbol)
+  }
+
+  override fun visitSymbol(node: Symbol) {
+    append(node.id)
+  }
+
+  override fun visitLambda(node: Lambda) {
+    append("{")
+    indent++
+    for (expression in node.expressions) {
+      appendLine()
+      indent()
+      visit(expression)
+    }
+
+    if (node.expressions.isNotEmpty()) {
+      appendLine()
+    }
+    indent--
+    indent()
+    append("}")
+  }
+
+  override fun visitIntLiteral(node: IntLiteral) {
+    append(node.value.toString())
+  }
+
+  override fun visitBooleanLiteral(node: BooleanLiteral) {
+    if (node.value) {
+      append("true")
+    } else {
+      append("false")
+    }
+  }
+
+  override fun visitListLiteral(node: ListLiteral) {
+    append("[")
+    for ((index, item) in node.items.withIndex()) {
+      visit(item)
+      if (index != node.items.size - 1) {
+        append(", ")
+      }
+    }
+    append("]")
+  }
+
+  override fun visitParentheses(node: Parentheses) {
+    append("(")
+    visit(node.expression)
+    append(")")
+  }
+
+  override fun visitInfixOperation(node: InfixOperation) {
+    visit(node.left)
+    append(" ")
+    append(node.op.token)
+    append(" ")
+    visit(node.right)
+  }
+
+  override fun visitProgram(node: Program) {
+    for (expression in node.expressions) {
+      indent()
+      visit(expression)
+      appendLine()
+    }
+  }
+}

src/main/kotlin/gay/pizza/pork/ast/Program.kt

@@ -0,0 +1,10 @@
+package gay.pizza.pork.ast
+
+class Program(val expressions: List<Expression>) : Node {
+  constructor(vararg expressions: Expression) : this(listOf(*expressions))
+
+  override val type: NodeType = NodeType.Program
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    expressions.map { visitor.visit(it) }
+}

src/main/kotlin/gay/pizza/pork/ast/Symbol.kt

@@ -0,0 +1,5 @@
+package gay.pizza.pork.ast
+
+class Symbol(val id: String) : Node {
+  override val type: NodeType = NodeType.Symbol
+}

src/main/kotlin/gay/pizza/pork/ast/SymbolReference.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.ast
+
+class SymbolReference(val symbol: Symbol) : Expression {
+  override val type: NodeType = NodeType.SymbolReference
+
+  override fun <T> visitChildren(visitor: Visitor<T>): List<T> =
+    listOf(visitor.visit(symbol))
+}

src/main/kotlin/gay/pizza/pork/ast/Visitor.kt

@@ -0,0 +1,38 @@
+package gay.pizza.pork.ast
+
+interface Visitor<T> {
+  fun visitDefine(node: Define): T
+  fun visitFunctionCall(node: FunctionCall): T
+  fun visitReference(node: SymbolReference): T
+  fun visitSymbol(node: Symbol): T
+  fun visitLambda(node: Lambda): T
+
+  fun visitIntLiteral(node: IntLiteral): T
+  fun visitBooleanLiteral(node: BooleanLiteral): T
+  fun visitListLiteral(node: ListLiteral): T
+
+  fun visitParentheses(node: Parentheses): T
+  fun visitInfixOperation(node: InfixOperation): T
+
+  fun visitProgram(node: Program): T
+
+  fun visitExpression(node: Expression): T = when (node) {
+    is IntLiteral -> visitIntLiteral(node)
+    is BooleanLiteral -> visitBooleanLiteral(node)
+    is ListLiteral -> visitListLiteral(node)
+    is Parentheses -> visitParentheses(node)
+    is InfixOperation -> visitInfixOperation(node)
+    is Define -> visitDefine(node)
+    is Lambda -> visitLambda(node)
+    is FunctionCall -> visitFunctionCall(node)
+    is SymbolReference -> visitReference(node)
+    else -> throw RuntimeException("Unknown Expression")
+  }
+
+  fun visit(node: Node): T = when (node) {
+    is Expression -> visitExpression(node)
+    is Symbol -> visitSymbol(node)
+    is Program -> visitProgram(node)
+    else -> throw RuntimeException("Unknown Node")
+  }
+}

src/main/kotlin/gay/pizza/pork/eval/Context.kt

@@ -0,0 +1,46 @@
+package gay.pizza.pork.eval
+
+import java.util.function.Function
+
+class Context(val parent: Context? = null) {
+  private val variables = mutableMapOf<String, Any>()
+
+  fun define(name: String, value: Any) {
+    if (variables.containsKey(name)) {
+      throw RuntimeException("Variable '${name}' is already defined.")
+    }
+    variables[name] = value
+  }
+
+  fun value(name: String): Any {
+    val value = variables[name]
+    if (value == null) {
+      if (parent != null) {
+        return parent.value(name)
+      }
+      throw RuntimeException("Variable '${name}' not defined.")
+    }
+    return value
+  }
+
+  fun call(name: String, argument: Any = Unit): Any {
+    val value = value(name)
+    if (value !is Function<*, *>) {
+      throw RuntimeException("$value is not callable.")
+    }
+    @Suppress("UNCHECKED_CAST")
+    val casted = value as Function<Any, Any>
+    return casted.apply(argument)
+  }
+
+  fun fork(): Context {
+    return Context(this)
+  }
+
+  fun leave(): Context {
+    if (parent == null) {
+      throw RuntimeException("Parent context not found.")
+    }
+    return parent
+  }
+}

src/main/kotlin/gay/pizza/pork/eval/Evaluator.kt

@@ -0,0 +1,71 @@
+package gay.pizza.pork.eval
+
+import gay.pizza.pork.ast.*
+import java.util.function.Function
+
+class Evaluator(root: Context) : Visitor<Any> {
+  private var currentContext: Context = root
+
+  override fun visitDefine(node: Define): Any {
+    val value = visit(node.value)
+    currentContext.define(node.symbol.id, value)
+    return value
+  }
+
+  override fun visitFunctionCall(node: FunctionCall): Any = currentContext.call(node.symbol.id)
+
+  override fun visitReference(node: SymbolReference): Any =
+    currentContext.value(node.symbol.id)
+
+  override fun visitSymbol(node: Symbol): Any {
+    return Unit
+  }
+
+  override fun visitLambda(node: Lambda): Function<Any, Any> {
+    return Function { _ ->
+      currentContext = currentContext.fork()
+      try {
+        var value: Any? = null
+        for (expression in node.expressions) {
+          value = visit(expression)
+        }
+        value ?: Unit
+      } finally {
+        currentContext = currentContext.leave()
+      }
+    }
+  }
+
+  override fun visitIntLiteral(node: IntLiteral): Any = node.value
+  override fun visitBooleanLiteral(node: BooleanLiteral): Any = node.value
+  override fun visitListLiteral(node: ListLiteral): Any = node.items.map { visit(it) }
+
+  override fun visitParentheses(node: Parentheses): Any = visit(node.expression)
+
+  override fun visitInfixOperation(node: InfixOperation): Any {
+    val left = visit(node.left)
+    val right = visit(node.right)
+
+    if (left !is Number || right !is Number) {
+      throw RuntimeException("Failed to evaluate infix operation, bad types.")
+    }
+
+    val leftInt = left.toInt()
+    val rightInt = right.toInt()
+
+    return when (node.op) {
+      InfixOperator.Plus -> leftInt + rightInt
+      InfixOperator.Minus -> leftInt - rightInt
+      InfixOperator.Multiply -> leftInt * rightInt
+      InfixOperator.Divide -> leftInt / rightInt
+    }
+  }
+
+  override fun visitProgram(node: Program): Any {
+    var value: Any? = null
+    for (expression in node.expressions) {
+      value = visit(expression)
+    }
+    return value ?: Unit
+  }
+}

src/main/kotlin/gay/pizza/pork/main.kt

@@ -0,0 +1,25 @@
+package gay.pizza.pork
+
+import gay.pizza.pork.ast.*
+import gay.pizza.pork.eval.Context
+import gay.pizza.pork.eval.Evaluator
+import gay.pizza.pork.parse.*
+import kotlin.io.path.Path
+import kotlin.io.path.readText
+
+fun main(args: Array<String>) {
+  fun eval(ast: Program) {
+    val context = Context()
+    val evaluator = Evaluator(context)
+    evaluator.visit(ast)
+    println("> ${context.call("main")}")
+  }
+
+  val code = Path(args[0]).readText()
+  val tokenizer = PorkTokenizer(StringCharSource(code))
+  val stream = tokenizer.tokenize()
+  println(stream.tokens.joinToString("\n"))
+  val parser = PorkParser(TokenStreamSource(stream))
+  val program = parser.readProgram()
+  eval(program)
+}

src/main/kotlin/gay/pizza/pork/parse/CharSource.kt

@@ -0,0 +1,8 @@
+package gay.pizza.pork.parse
+
+interface CharSource : PeekableSource<Char> {
+  companion object {
+    @Suppress("ConstPropertyName")
+    const val NullChar = 0.toChar()
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/PeekableSource.kt

@@ -0,0 +1,7 @@
+package gay.pizza.pork.parse
+
+interface PeekableSource<T> {
+  val currentIndex: Int
+  fun next(): T
+  fun peek(): T
+}

src/main/kotlin/gay/pizza/pork/parse/PorkParser.kt

@@ -0,0 +1,125 @@
+package gay.pizza.pork.parse
+
+import gay.pizza.pork.ast.*
+
+class PorkParser(val source: PeekableSource<Token>) {
+  private fun readIntLiteral(): IntLiteral {
+    val token = expect(TokenType.IntLiteral)
+    return IntLiteral(token.text.toInt())
+  }
+
+  private fun readSymbol(): Symbol {
+    val token = expect(TokenType.Symbol)
+    return Symbol(token.text)
+  }
+
+  private fun readSymbolCases(): Expression {
+    val symbol = readSymbol()
+    return if (peekType(TokenType.LeftParentheses)) {
+      expect(TokenType.LeftParentheses)
+      expect(TokenType.RightParentheses)
+      FunctionCall(symbol)
+    } else if (peekType(TokenType.Equals)) {
+      expect(TokenType.Equals)
+      Define(symbol, readExpression())
+    } else {
+      SymbolReference(symbol)
+    }
+  }
+
+  fun readLambda(): Lambda {
+    expect(TokenType.LeftCurly)
+    val items = collectExpressions(TokenType.RightCurly)
+    expect(TokenType.RightCurly)
+    return Lambda(items)
+  }
+
+  fun readExpression(): Expression {
+    val token = source.peek()
+    val expression = when (token.type) {
+      TokenType.IntLiteral -> {
+        readIntLiteral()
+      }
+      TokenType.LeftBracket -> {
+        readListLiteral()
+      }
+      TokenType.Symbol -> {
+        readSymbolCases()
+      }
+      TokenType.LeftCurly -> {
+        readLambda()
+      }
+      TokenType.LeftParentheses -> {
+        expect(TokenType.LeftParentheses)
+        val expression = readExpression()
+        expect(TokenType.RightParentheses)
+        Parentheses(expression)
+      }
+      TokenType.True -> {
+        expect(TokenType.True)
+        return BooleanLiteral(true)
+      }
+      TokenType.False -> {
+        expect(TokenType.False)
+        return BooleanLiteral(false)
+      }
+      else -> {
+        throw RuntimeException("Failed to parse token: ${token.type} '${token.text}' as expression.")
+      }
+    }
+
+    if (peekType(TokenType.Plus, TokenType.Minus, TokenType.Multiply, TokenType.Divide)) {
+      val infixToken = source.next()
+      val infixOperator = convertInfixOperator(infixToken)
+      return InfixOperation(expression, infixOperator, readExpression())
+    }
+    return expression
+  }
+
+  private fun convertInfixOperator(token: Token): InfixOperator =
+    when (token.type) {
+      TokenType.Plus -> InfixOperator.Plus
+      TokenType.Minus -> InfixOperator.Minus
+      TokenType.Multiply -> InfixOperator.Multiply
+      TokenType.Divide -> InfixOperator.Divide
+      else -> throw RuntimeException("Unknown Infix Operator")
+    }
+
+  fun readListLiteral(): ListLiteral {
+    expect(TokenType.LeftBracket)
+    val items = collectExpressions(TokenType.RightBracket, TokenType.Comma)
+    expect(TokenType.RightBracket)
+    return ListLiteral(items)
+  }
+
+  fun readProgram(): Program {
+    val items = collectExpressions(TokenType.EndOfFile)
+    expect(TokenType.EndOfFile)
+    return Program(items)
+  }
+
+  private fun collectExpressions(peeking: TokenType, consuming: TokenType? = null): List<Expression> {
+    val items = mutableListOf<Expression>()
+    while (!peekType(peeking)) {
+      val expression = readExpression()
+      if (consuming != null && !peekType(peeking)) {
+        expect(consuming)
+      }
+      items.add(expression)
+    }
+    return items
+  }
+
+  private fun peekType(vararg types: TokenType): Boolean {
+    val token = source.peek()
+    return types.contains(token.type)
+  }
+
+  private fun expect(type: TokenType): Token {
+    val token = source.next()
+    if (token.type != type) {
+      throw RuntimeException("Expected token type '${type}' but got type ${token.type} '${token.text}'")
+    }
+    return token
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/PorkTokenizer.kt

@@ -0,0 +1,87 @@
+package gay.pizza.pork.parse
+
+class PorkTokenizer(val source: CharSource) {
+  private var tokenStart: Int = 0
+
+  private fun isSymbol(c: Char): Boolean =
+    (c in 'a'..'z') || (c in 'A'..'Z') || c == '_'
+
+  private fun isDigit(c: Char): Boolean =
+    c in '0'..'9'
+
+  private fun isWhitespace(c: Char): Boolean =
+    c == ' ' || c == '\r' || c == '\n' || c == '\t'
+
+  private fun readSymbolOrKeyword(firstChar: Char): Token {
+    val symbol = buildString {
+      append(firstChar)
+      while (isSymbol(source.peek())) {
+        append(source.next())
+      }
+    }
+
+    var type = TokenType.Symbol
+    for (keyword in TokenType.Keywords) {
+      if (symbol == keyword.keyword) {
+        type = keyword
+      }
+    }
+
+    return Token(type, symbol)
+  }
+
+  private fun readIntLiteral(firstChar: Char): Token {
+    val number = buildString {
+      append(firstChar)
+      while (isDigit(source.peek())) {
+        append(source.next())
+      }
+    }
+    return Token(TokenType.IntLiteral, number)
+  }
+
+  private fun skipWhitespace() {
+    while (isWhitespace(source.peek())) {
+      source.next()
+    }
+  }
+
+  fun next(): Token {
+    while (source.peek() != CharSource.NullChar) {
+      tokenStart = source.currentIndex
+      val char = source.next()
+      for (item in TokenType.SingleChars) {
+        if (item.singleChar == char) {
+          return Token(item, char.toString())
+        }
+      }
+
+      if (isWhitespace(char)) {
+        skipWhitespace()
+        continue
+      }
+
+      if (isDigit(char)) {
+        return readIntLiteral(char)
+      }
+
+      if (isSymbol(char)) {
+        return readSymbolOrKeyword(char)
+      }
+      throw RuntimeException("Failed to parse: (${char}) next ${source.peek()}")
+    }
+    return TokenSource.EndOfFile
+  }
+
+  fun tokenize(): TokenStream {
+    val tokens = mutableListOf<Token>()
+    while (true) {
+      val token = next()
+      tokens.add(token)
+      if (token.type == TokenType.EndOfFile) {
+        break
+      }
+    }
+    return TokenStream(tokens)
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/StringCharSource.kt

@@ -0,0 +1,22 @@
+package gay.pizza.pork.parse
+
+class StringCharSource(val input: String) : CharSource {
+  private var index = 0
+  override val currentIndex: Int = index
+
+  override fun next(): Char {
+    if (index == input.length) {
+      return CharSource.NullChar
+    }
+    val char = input[index]
+    index++
+    return char
+  }
+
+  override fun peek(): Char {
+    if (index == input.length) {
+      return CharSource.NullChar
+    }
+    return input[index]
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/Token.kt

@@ -0,0 +1,5 @@
+package gay.pizza.pork.parse
+
+class Token(val type: TokenType, val text: String) {
+  override fun toString(): String = "${type.name} $text"
+}

src/main/kotlin/gay/pizza/pork/parse/TokenSource.kt

@@ -0,0 +1,7 @@
+package gay.pizza.pork.parse
+
+interface TokenSource : PeekableSource<Token> {
+  companion object {
+    val EndOfFile = Token(TokenType.EndOfFile, "")
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/TokenStream.kt

@@ -0,0 +1,5 @@
+package gay.pizza.pork.parse
+
+class TokenStream(val tokens: List<Token>) {
+  override fun toString(): String = tokens.toString()
+}

src/main/kotlin/gay/pizza/pork/parse/TokenStreamSource.kt

@@ -0,0 +1,22 @@
+package gay.pizza.pork.parse
+
+class TokenStreamSource(val stream: TokenStream) : TokenSource {
+  private var index = 0
+  override val currentIndex: Int = index
+
+  override fun next(): Token {
+    if (index == stream.tokens.size) {
+      return TokenSource.EndOfFile
+    }
+    val char = stream.tokens[index]
+    index++
+    return char
+  }
+
+  override fun peek(): Token {
+    if (index == stream.tokens.size) {
+      return TokenSource.EndOfFile
+    }
+    return stream.tokens[index]
+  }
+}

src/main/kotlin/gay/pizza/pork/parse/TokenType.kt

@@ -0,0 +1,26 @@
+package gay.pizza.pork.parse
+
+enum class TokenType(val singleChar: Char? = null, val keyword: String? = null) {
+  Symbol,
+  IntLiteral,
+  Equals(singleChar = '='),
+  Plus(singleChar = '+'),
+  Minus(singleChar = '-'),
+  Multiply(singleChar = '*'),
+  Divide(singleChar = '/'),
+  LeftCurly(singleChar = '{'),
+  RightCurly(singleChar = '}'),
+  LeftBracket(singleChar = '['),
+  RightBracket(singleChar = ']'),
+  LeftParentheses(singleChar = '('),
+  RightParentheses(singleChar = ')'),
+  Comma(singleChar = ','),
+  False(keyword = "false"),
+  True(keyword = "true"),
+  EndOfFile;
+
+  companion object {
+    val Keywords = entries.filter { it.keyword != null }
+    val SingleChars = entries.filter { it.singleChar != null }
+  }
+}