Ast.java

package frontend.syntax;

import frontend.lexer.Token;
import frontend.lexer.TokenType;

import java.util.ArrayList;

/**
 * 所有的语法树节点
 * 为简化编译器实现难度, 对文法进行了改写(不影响语义)
 */
public class Ast {

    public ArrayList<CompUnit> units;

    // CompUnit -> Decl | FuncDef
    public interface CompUnit {
    }

    // Decl -> ['const'] 'int' Def {',' Def} ';'
    public static class Decl implements CompUnit, BlockItem {

        public boolean constant;
        public Token bType;
        public ArrayList<Def> defs;

        public Decl(boolean constant, Token bType, ArrayList<Def> defs) {
            assert bType != null;
            assert defs != null;
            this.constant = constant;
            this.bType = bType;
            this.defs = defs;
        }

        public boolean isConstant() {
            return this.constant;
        }

        public Token getBType() {
            return bType;
        }

        public ArrayList<Def> getDefs() {
            return defs;
        }
    }

    // Def -> Ident {'[' Exp ']'} ['=' Init]
    public static class Def {

        public TokenType bType;
        public Token ident;
        public ArrayList<Exp> indexes;
        public Init init;

        public Def(TokenType bType, Token ident, ArrayList<Exp> indexes, Init init) {
            assert bType != null;
            assert ident != null;
            assert indexes != null;
            // assert init != null;
            this.bType = bType;
            this.ident = ident;
            this.indexes = indexes;
            this.init = init;
        }

        public Token getIdent() {
            return this.ident;
        }