Initial commit

java/com/craftinginterpreters/tool/GenerateAst.java

@@ -0,0 +1,93 @@
+package com.craftinginterpreters.tool;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.Arrays;
+import java.util.List;
+
+public class GenerateAst {
+  public static void main(String[] args) throws IOException {
+    // if (args.length != 1) {
+    // System.err.println("Usage: generate_ast <output directory>");
+    // System.exit(64);
+    // }
+    // String outputDir = args[0];
+    String outputDir = "com/craftinginterpreters/lox";
+    defineAst(outputDir, "Expr", Arrays.asList(
+        "Binary   : Expr left, Token operator, Expr right",
+        "Grouping : Expr expression",
+        "Literal  : Object value",
+        "Unary    : Token operator, Expr right"));
+  }
+
+  private static void defineAst(
+      String outputDir, String baseName, List<String> types) throws IOException {
+    String path = outputDir + "/" + baseName + ".java";
+    PrintWriter writer = new PrintWriter(path, "UTF-8");
+
+    writer.println("package com.craftinginterpreters.lox;");
+    writer.println();
+    writer.println("import java.util.List;");
+    writer.println();
+    writer.println("abstract class " + baseName + " {");
+
+    defineVisitor(writer, baseName, types);
+
+    // The AST clasess.
+    for (String type : types) {
+      String className = type.split(":")[0].trim();
+      String fields = type.split(":")[1].trim();
+      defineType(writer, baseName, className, fields);
+    }
+
+    // The base accept() method.
+    writer.println("  abstract <R> R accept(Visitor<R> visitor);");
+
+    writer.println("}");
+    writer.close();
+  }
+
+  private static void defineVisitor(PrintWriter writer, String baseName, List<String> types) {
+    writer.println("  interface Visitor<R> {");
+
+    for (String type : types) {
+      String typeName = type.split(":")[0].trim();
+      writer.println("    R visit" + typeName + baseName + "(" + typeName + " " + baseName.toLowerCase() + ");");
+    }
+
+    writer.println("  }");
+    writer.println();
+  }
+
+  private static void defineType(PrintWriter writer, String baseName, String className, String fieldList) {
+    writer.println("  static class " + className + " extends " + baseName + " {");
+
+    // Constructor.
+    writer.println("    " + className + "(" + fieldList + ") {");
+
+    // Store parameters in fields.
+    String[] fields = fieldList.split(", ");
+    for (String field : fields) {
+      String name = field.split(" ")[1];
+      writer.println("      this." + name + " = " + name + ";");
+    }
+
+    writer.println("    }");
+
+    // Visitor pattern.
+    writer.println();
+    writer.println("    @Override");
+    writer.println("    <R> R accept(Visitor<R> visitor) {");
+    writer.println("      return visitor.visit" + className + baseName + "(this);");
+    writer.println("    }");
+
+    // Fields.
+    writer.println();
+    for (String field : fields) {
+      writer.println("    final " + field + ";");
+    }
+
+    writer.println("  }");
+    writer.println();
+  }
+}