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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];
defineAst(outputDir, "Expr",
Arrays.asList("Assign : Token name, Expr value", "Binary : Expr left, Token operator, Expr right",
"Grouping : Expr expression", "Literal : Object value",
"Logical : Expr left, Token operator, Expr right", "Unary : Token operator, Expr right",
"Variable : Token name"));
defineAst(outputDir, "Stmt",
Arrays.asList("Block : List<Stmt> statements", "Expression : Expr expression",
"If : Expr condition, Stmt thenBranch, Stmt elseBranch", "Print : Expr expression",
"Var : Token name, Expr initializer"));
}
private static void defineAst(String outputDir, String baseName, List<String> types) throws IOException {
String path = outputDir + "/" + baseName + ".java";
PrintWriter writer = new PrintWriter(path);
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);
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();
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(" }");
}
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(" }");
}
}
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