diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 3e4bbe1..98ab86d 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -5,7 +5,8 @@
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleHome" value="$USER_HOME$/.sdkman/candidates/gradle/8.5" />
+        <option name="gradleHome" value="/usr/local/Cellar/gradle/8.8_1/libexec" />
+        <option name="gradleJvm" value="corretto-21" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
diff --git a/build.gradle.kts b/build.gradle.kts
index 0f1053f..9c80e75 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -11,6 +11,7 @@ repositories {
 
 dependencies {
     testImplementation(kotlin("test"))
+    implementation(kotlin("script-runtime"))
 }
 
 sourceSets {
diff --git a/src/main/ExprGenerator.ws.kts b/src/main/ExprGenerator.ws.kts
new file mode 100644
index 0000000..314a92a
--- /dev/null
+++ b/src/main/ExprGenerator.ws.kts
@@ -0,0 +1,27 @@
+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")
+println()
+println("sealed class Expr {")
+println("}")
+
+for (type in types) {
+    val parts = type.split(":")
+    val name = parts[0].trim()
+    val fields = parts[1].trim().split(",").map { it.trim() }
+    println()
+    println("data class $name(")
+    for (field in fields) {
+        val parts = field.split(" ")
+        val type = parts[0]
+        val name = parts[1]
+        val sep = if (field == fields.last()) "" else ","
+        println("    val $name: $type$sep")
+    }
+    println(") : Expr()")
+}
\ No newline at end of file
diff --git a/src/main/fr/celticinfo/lox/Expr.kt b/src/main/fr/celticinfo/lox/Expr.kt
new file mode 100644
index 0000000..6a245b8
--- /dev/null
+++ b/src/main/fr/celticinfo/lox/Expr.kt
@@ -0,0 +1,23 @@
+package fr.celticinfo.lox
+
+sealed class Expr {
+}
+
+data class Binary(
+    val left: Expr,
+    val operator: Token,
+    val right: Expr
+) : Expr()
+
+data class Grouping(
+    val expression: Expr
+) : Expr()
+
+data class Literal(
+    val value: Any
+) : Expr()
+
+data class Unary(
+    val operator: Token,
+    val right: Expr
+) : Expr()
\ No newline at end of file