从解析器创建抽象树问题

我需要很大的帮助，我有两个简单的类Tree和Node（我只是在界面上使用较少的空间，我可以轻松修改那些类），我也有flex文件和解析器文件，需要创建AST（抽象语法树 – 在Node对象中放置标记并以正确的方式填充Tree）。

public class Tree { Node root; public void AddNode(Node n){} public void Evaluate(){} } public class Node { public String value; public int type; Node left, right; } 

这是解析器文件

 import java_cup.runtime.*; parser code {: public boolean result = true; public void report_fatal_error(String message, Object info) throws java.lang.Exception { done_parsing(); System.out.println("report_fatal_error"); report_error(); } public void syntax_error(Symbol cur_token) { System.out.println("syntax_error"); report_error(); } public void unrecovered_syntax_error(Symbol cur_token) throws java.lang.Exception { System.out.println("unrecovered_syntax_error"); report_fatal_error("Fatalna greska, parsiranje se ne moze nastaviti", cur_token); } public void report_error(){ System.out.println("report_error"); result = false; } :} init with {: result = true; :}; /* Terminals (tokens returned by the scanner). */ terminal AND, OR, NOT; terminal LPAREN, RPAREN; terminal ITEM; terminal OPEN, CLOSE, MON, MOFF, TIMEOUT, ESERR, BAE, I, O, BUS, EXT, PUSHB; terminal VAL, OK, BUS_BR_L, BUS_BR_R, SH_CRT_L, SH_CRT_R, BUS_ALL, EXT_ALL, NO_TIMEOUT, NO_ES_ERR, IBUS_OK, CFG_OK, SYNTAX; terminal OUT; /* Non-terminals */ non terminal extension; non terminal Integer expr; /* Precedences */ precedence left AND, OR; /* The grammar */ expr ::= | expr:e1 AND expr:e2 {: //System.out.println("AND"); RESULT = 1; :} | expr:e1 OR expr:e2 {: //System.out.println("OR"); RESULT = 2; :} | NOT expr:e1 {: //System.out.println("NOT"); RESULT = 3; :} | LPAREN expr:e RPAREN {: //System.out.println("()"); RESULT = 4; :} | ITEM extension:e1 {: //System.out.println("ITEM."); RESULT = 5; :} | error {: System.out.println("error"); parser.report_error(); RESULT = 0; :} ; extension ::= OPEN | MON | CLOSE | MOFF | TIMEOUT | ESERR | BAE | I | O | BUS | EXT | PUSHB | VAL | OK | BUS_BR_L | BUS_BR_R | SH_CRT_L | SH_CRT_R | BUS_ALL | EXT_ALL | NO_TIMEOUT | NO_ES_ERR | IBUS_OK | CFG_OK | SYNTAX | OUT ; 

这是语法

 %% %{ public boolean result = true; //Puni expression sa tokenima radi reimenovanja public Expression expression=new Expression(); // public ArrayList items = new ArrayList(); public ArrayList extensions = new ArrayList(); // ukljucivanje informacije o poziciji tokena private Symbol new_symbol(int type) { return new Symbol(type, yyline+1, yycolumn); } // ukljucivanje informacije o poziciji tokena private Symbol new_symbol(int type, Object value) { return new Symbol(type, yyline+1, yycolumn, value); } %} %cup %xstate COMMENT %eofval{ return new_symbol(sym.EOF); %eofval} %line %column %% " " {} "\b" {} "\t" {} "\r\n" {} "\f" {} "open" {extensions.add(sym.OPEN); return new_symbol(sym.OPEN);} "close" {extensions.add(sym.CLOSE); return new_symbol(sym.CLOSE);} "m_on" {extensions.add(sym.MON); return new_symbol(sym.MON);} "m_off" {extensions.add(sym.MOFF); return new_symbol(sym.MOFF);} "timeout" {extensions.add(sym.TIMEOUT); return new_symbol(sym.TIMEOUT);} "es_err" {extensions.add(sym.ESERR); return new_symbol(sym.ESERR);} "bae" {extensions.add(sym.BAE); return new_symbol(sym.BAE);} "i" {extensions.add(sym.I); return new_symbol(sym.I);} "o" {extensions.add(sym.O); return new_symbol(sym.O);} "bus" {extensions.add(sym.BUS); return new_symbol(sym.BUS);} "ext" {extensions.add(sym.EXT); return new_symbol(sym.EXT);} "pushb" {extensions.add(sym.PUSHB); return new_symbol(sym.PUSHB);} "val" {extensions.add(sym.VAL); return new_symbol(sym.VAL);} "ok" {extensions.add(sym.OK); return new_symbol(sym.OK);} "bus_br_l" {extensions.add(sym.BUS_BR_L); return new_symbol(sym.BUS_BR_L);} "bus_br_r" {extensions.add(sym.BUS_BR_R); return new_symbol(sym.BUS_BR_R);} "sh_crt_l" {extensions.add(sym.SH_CRT_L); return new_symbol(sym.SH_CRT_L);} "sh_crt_r" {extensions.add(sym.SH_CRT_R); return new_symbol(sym.SH_CRT_R);} "bus_all" {extensions.add(sym.BUS_ALL); return new_symbol(sym.BUS_ALL);} "ext_all" {extensions.add(sym.EXT_ALL); return new_symbol(sym.EXT_ALL);} "no_timeout" {extensions.add(sym.NO_TIMEOUT); return new_symbol(sym.NO_TIMEOUT);} "no_es_err" {extensions.add(sym.NO_ES_ERR); return new_symbol(sym.NO_ES_ERR);} "ibus_ok" {extensions.add(sym.IBUS_OK); return new_symbol(sym.IBUS_OK);} "cfg_ok" {extensions.add(sym.CFG_OK); return new_symbol(sym.CFG_OK);} "syntax" {extensions.add(sym.SYNTAX); return new_symbol(sym.SYNTAX);} "out" {extensions.add(sym.OUT); return new_symbol(sym.OUT);} "!" { return new_symbol(sym.NOT);} "&" { return new_symbol(sym.AND);} "|" { return new_symbol(sym.OR);} "(" { return new_symbol(sym.LPAREN);} ")" { return new_symbol(sym.RPAREN);} ([[:jletter:]])[[:jletterdigit:]]* \. {items.add(yytext().substring(0, yytext().length()-1)); return new_symbol (sym.ITEM);} . {result = false;} 

Probem是如何从这里创建AST的，我得到了类似的输入表达式

A.open && bi？ 有人可以帮忙吗？

Answer 1

在您的Parser中您注释掉了以下打印语句的行：

  //System.out.println("OR"); 

是您希望使用Tree数据结构维护AST的地方。 根据您的语法找出将创建树的令牌，在树中的某处添加内容等。