Added Stmt class

src/main/ExprGenerator.ws.kts

@@ -1,31 +1,22 @@
 import java.util.*
 
-val types = listOf(
-    "Binary   : Expr left, Token operator, Expr right",
-    "Grouping : Expr expression",
-    "Literal  : Any? value",
-    "Unary    : Token operator, Expr right"
-)
-
-println("package fr.celticinfo.lox")
+fun defineAst(baseName: String, types: List<String>) {
+    println("package fr.celticinfo.lox")
 
-println()
-println("interface ExprVisitor<R> {")
-for (type in types) {
+    println()
+    println("interface ${baseName}Visitor<R> {")
+    for (type in types) {
         val parts = type.split(":")
         val name = parts[0].trim()
-    println("    fun visit$name(${name.lowercase(Locale.getDefault())}: $name): R")
-}
-println("}")
+        println("    fun visit$name(${baseName.lowercase(Locale.getDefault())}: $name): R")
+    }
+    println("}")
 
-println()
-println("""/**
- * The Expr class represents the different types of expressions that can be parsed by the Parser.
- */""".trimIndent())
-println("sealed class Expr {")
-println("    abstract fun <R> accept(visitor: ExprVisitor<R>): R")
-println("}")
-for (type in types) {
+    println()
+    println("sealed class $baseName {")
+    println("    abstract fun <R> accept(visitor: ${baseName}Visitor<R>): R")
+    println("}")
+    for (type in types) {
         val parts = type.split(":")
         val name = parts[0].trim()
         val fields = parts[1].trim().split(",").map { it.trim() }
@@ -38,9 +29,26 @@ for (type in types) {
             val sep = if (field == fields.last()) "" else ","
             println("    val $fname: $ftype$sep")
         }
-    println(") : Expr() {")
-    println("    override fun <R> accept(visitor: ExprVisitor<R>): R {")
+        println(") : ${baseName}() {")
+        println("    override fun <R> accept(visitor: ${baseName}Visitor<R>): R {")
         println("        return visitor.visit$name(this)")
         println("    }")
         println("}")
+    }
+
+
 }
+
+val exprTypes = listOf(
+    "Binary   : Expr left, Token operator, Expr right",
+    "Grouping : Expr expression",
+    "Literal  : Any? value",
+    "Unary    : Token operator, Expr right"
+)
+defineAst("Expr", exprTypes)
+
+val stmtTypes = listOf(
+    "Expression : Expr expression",
+    "Print      : Expr expression"
+)
+defineAst("Stmt", stmtTypes)

src/main/fr/celticinfo/lox/Expr.kt

@@ -1,11 +1,13 @@
 package fr.celticinfo.lox
 
+/**
+ * The ExprVisitor interface is used to visit the different types of expressions that can be parsed by the Parser.
+ */
 interface ExprVisitor<R> {
-    fun visitBinary(binary: Binary): R
-    fun visitGrouping(grouping: Grouping): R
-    fun visitLiteral(literal: Literal): R
-    fun visitUnary(unary: Unary): R
-
+    fun visitBinary(expr: Binary): R
+    fun visitGrouping(expr: Grouping): R
+    fun visitLiteral(expr: Literal): R
+    fun visitUnary(expr: Unary): R
 }
 
 /**

src/main/fr/celticinfo/lox/Interpreter.kt

@@ -2,41 +2,54 @@ package fr.celticinfo.lox
 
 import fr.celticinfo.lox.TokenType.*
 
-class Interpreter: ExprVisitor<Any?>{
+class Interpreter: ExprVisitor<Any?>, StmtVisitor<Unit>{
 
-    fun interpret(expr: Expr): Any? {
-        return try {
-            val value = evaluate(expr)
-            println(stringify(value))
-            value
+    fun interpret(statements: List<Stmt>) {
+        try {
+            for (statement in statements) {
+                execute(statement)
+            }
         } catch (error: RuntimeError) {
             Lox.runtimeError(error)
-            null
+            throw error
         }
     }
 
+    private fun execute(stmt: Stmt) {
+        stmt.accept(this)
+    }
+
     private fun evaluate(expr: Expr): Any? {
         return expr.accept(this)
     }
 
-    override fun visitBinary(binary: Binary): Any? {
-        val left = evaluate(binary.left)
-        val right = evaluate(binary.right)
+    override fun visitExpression(stmt: Expression) {
+        evaluate(stmt.expression)
+    }
+
+    override fun visitPrint(stmt: Print) {
+        val value = evaluate(stmt.expression)
+        println(stringify(value))
+    }
+
+    override fun visitBinary(expr: Binary): Any? {
+        val left = evaluate(expr.left)
+        val right = evaluate(expr.right)
 
-        return when (binary.operator.type) {
+        return when (expr.operator.type) {
             MINUS -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 left as Double - right as Double
             }
             SLASH -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 if (right == 0.0) {
-                    throw RuntimeError(binary.operator, "Division by zero")
+                    throw RuntimeError(expr.operator, "Division by zero")
                 }
                 left as Double / right as Double
             }
             STAR -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 left as Double * right as Double
             }
             PLUS -> {
@@ -45,23 +58,23 @@ class Interpreter: ExprVisitor<Any?>{
                 } else if (left is String && right is String) {
                     left + right
                 } else {
-                    throw RuntimeError(binary.operator, "Operands must be two numbers or two strings")
+                    throw RuntimeError(expr.operator, "Operands must be two numbers or two strings")
                 }
             }
             GREATER -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 left as Double > right as Double
             }
             GREATER_EQUAL -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 left as Double >= right as Double
             }
             LESS -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 (left as Double) < right as Double
             }
             LESS_EQUAL -> {
-                checkNumberOperands(binary.operator, left, right)
+                checkNumberOperands(expr.operator, left, right)
                 left as Double <= right as Double
             }
             BANG_EQUAL -> return !isEqual(left, right)
@@ -70,20 +83,20 @@ class Interpreter: ExprVisitor<Any?>{
         }
     }
 
-    override fun visitGrouping(grouping: Grouping): Any? {
-        return evaluate(grouping.expression)
+    override fun visitGrouping(expr: Grouping): Any? {
+        return evaluate(expr.expression)
     }
 
-    override fun visitLiteral(literal: Literal): Any? {
-        return literal.value
+    override fun visitLiteral(expr: Literal): Any? {
+        return expr.value
     }
 
-    override fun visitUnary(unary: Unary): Any? {
-        val right = evaluate(unary.right)
+    override fun visitUnary(expr: Unary): Any? {
+        val right = evaluate(expr.right)
 
-        return when (unary.operator.type) {
+        return when (expr.operator.type) {
             MINUS -> {
-                checkNumberOperand(unary.operator, right)
+                checkNumberOperand(expr.operator, right)
                 -(right as Double)
             }
             BANG -> !isTruthy(right)

src/main/fr/celticinfo/lox/Lox.kt

@@ -40,12 +40,12 @@ object Lox {
         val scanner = Scanner(source)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expression = parser.parse()
+        val statements = parser.parse()
 
         // Stop if there was a syntax error.
         if (hadError) return
 
-        interpreter.interpret(expression!!)
+        interpreter.interpret(statements)
     }
 
     fun error(line: Int, s: String) {

src/main/fr/celticinfo/lox/Parser.kt

@@ -2,6 +2,7 @@ package fr.celticinfo.lox
 
 import fr.celticinfo.lox.TokenType.*
 
+
 /**
  * The Parser class is responsible for parsing the tokens produced by the Scanner into an abstract syntax tree (AST).
  * It is a recursive descent parser that uses a series of methods to parse different parts of the grammar.
@@ -9,18 +10,32 @@ import fr.celticinfo.lox.TokenType.*
 class Parser(private val tokens: List<Token>) {
     private var current = 0
 
-    fun parse(): Expr? {
-        return try {
-            val result = expression()
+    fun parse(): List<Stmt> {
+        val statements: MutableList<Stmt> = ArrayList()
+        while (!isAtEnd()) {
+            statements.add(statement())
+        }
 
-            if (!isAtEnd()) {
-                throw error(peek(), "Expect end of expression.")
+        return statements
     }
 
-            result
-        } catch (error: ParseError) {
-            null
+    private fun statement(): Stmt {
+        return when {
+            match(PRINT) -> printStatement()
+            else -> expressionStatement()
+        }
     }
+
+    private fun printStatement(): Stmt {
+        val value = expression()
+        consume(SEMICOLON, "Expect ';' after value.")
+        return Print(value)
+    }
+
+    private fun expressionStatement(): Stmt {
+        val value = expression()
+        consume(SEMICOLON, "Expect ';' after value.")
+        return Expression(value)
     }
 
     private fun expression(): Expr {

src/main/fr/celticinfo/lox/Stmt.kt

@@ -0,0 +1,32 @@
+package fr.celticinfo.lox
+
+/**
+ * The StmtVisitor interface is used to visit the different types of statements that can be parsed by the Parser.
+ */
+interface StmtVisitor<R> {
+    fun visitExpression(stmt: Expression): R
+    fun visitPrint(stmt: Print): R
+}
+
+/**
+ * The Stmt class represents the different types of statements that can be parsed by the Parser.
+ */
+sealed class Stmt {
+    abstract fun <R> accept(visitor: StmtVisitor<R>): R
+}
+
+data class Expression(
+    val expression: Expr
+) : Stmt() {
+    override fun <R> accept(visitor: StmtVisitor<R>): R {
+        return visitor.visitExpression(this)
+    }
+}
+
+data class Print(
+    val expression: Expr
+) : Stmt() {
+    override fun <R> accept(visitor: StmtVisitor<R>): R {
+        return visitor.visitPrint(this)
+    }
+}

src/test/fr/celticinfo/lox/InterpreterTest.kt

@@ -1,46 +1,60 @@
 package fr.celticinfo.lox
 
+import fr.celticinfo.loxext.RpnPrinter
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.Assertions.*
+import kotlin.test.*
 
 class InterpreterTest {
 
     @Test
     fun `validate interpreter`() {
         val code = """
-            (1 + 2 * 3 - 5) / 2
+            1 + 2 * 3 - 4 / 5;
         """.trimIndent()
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        val value = Interpreter().interpret(expr!!)
-        assertEquals(1.0, value)
+        val statements = parser.parse()
+        assertEquals(1, statements.size)
+        val stmt = statements.first()
+        assertTrue(stmt is Expression)
+        val expr = stmt.expression
+        assertEquals("1.0 2.0 3.0 * + 4.0 5.0 / -", RpnPrinter().print(expr))
     }
 
     @Test
     fun `Division by zero should raise error`() {
         val code = """
-            1 / 0
+            1 / 0;
         """.trimIndent()
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        val value = Interpreter().interpret(expr!!)
-        assertNull(value)
+        val statements = parser.parse()
+        assertEquals(1, statements.size)
+
+        assertFailsWith<RuntimeError>(
+            block = {
+                Interpreter().interpret(statements)
+            }
+        )
     }
 
     @Test
     fun `Invalid type raise error`() {
         val code = """
-            1 + false
+            1 + false;
         """.trimIndent()
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        val value = Interpreter().interpret(expr!!)
-        assertNull(value)
+        val statements = parser.parse()
+        assertEquals(1, statements.size)
+
+        assertFailsWith<RuntimeError>(
+            block = {
+                Interpreter().interpret(statements)
+            }
+        )
     }
 }

src/test/fr/celticinfo/lox/ParserTest.kt

@@ -2,20 +2,23 @@ package fr.celticinfo.lox
 
 import fr.celticinfo.loxext.RpnPrinter
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.Assertions.*
+import kotlin.test.*
 
 class ParserTest {
     @Test
     fun `validate parser`() {
         val code = """
-            1 + 2 * 3 - 4 / 5
+            1 + 2 * 3 - 4 / 5;
         """.trimIndent()
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        assertNotNull(expr)
-        assertEquals("1.0 2.0 3.0 * + 4.0 5.0 / -", RpnPrinter().print(expr!!))
+        val statements = parser.parse()
+        assertEquals(1,statements.size)
+        val stmt = statements.first()
+        assertTrue(stmt is Expression)
+        val expr = stmt.expression
+        assertEquals("1.0 2.0 3.0 * + 4.0 5.0 / -", RpnPrinter().print(expr))
     }
 
     @Test
@@ -26,8 +29,12 @@ class ParserTest {
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        assertNull(expr)
+
+        assertFailsWith<Parser.ParseError>(
+            block = {
+                parser.parse()
+            }
+        )
     }
 
     @Test
@@ -38,7 +45,11 @@ class ParserTest {
         val scanner = Scanner(code)
         val tokens = scanner.scanTokens()
         val parser = Parser(tokens)
-        val expr = parser.parse()
-        assertNull(expr)
+
+        assertFailsWith<Parser.ParseError>(
+            block = {
+                parser.parse()
+            }
+        )
     }
 }