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我想第一次嘗試javacc與一個簡單樸素的例子,這是不工作。我的BNF如下:使用上述文件JavaCC簡單的例子不工作
options
{
}
PARSER_BEGIN(SimpleAdd)
public class SimpleAdd
{
}
PARSER_END(SimpleAdd)
SKIP :
{
" "
| "\r"
| "\t"
| "\n"
}
TOKEN:
{
< NUMBER: (["0"-"9"])+ >
}
int expr():
{
int leftValue ;
int rightValue ;
}
{
leftValue = num()
"+"
rightValue = num()
{ return leftValue+rightValue; }
}
int num():
{
Token t;
}
{
t = <NUMBER> { return Integer.parseInt(t.toString()); }
}
,我生成Java源代碼類:
<exp>:= <num>"+"<num>
<num>:= <digit> | <digit><num>
<digit>:= [0-9]
在此基礎上BNF,我寫了SimpleAdd.jj
如下。我的主類是如下:
public class Main {
public static void main(String [] args) throws ParseException {
SimpleAdd parser = new SimpleAdd(System.in);
int x = parser.expr();
System.out.println(x);
}
}
當我進入通過System.in表達,我收到以下錯誤:
11+11^D
Exception in thread "main" SimpleAddTest.ParseException: Encountered "<EOF>" at line 0, column 0.
Was expecting:
<NUMBER> ...
at SimpleAddTest.SimpleAdd.generateParseException(SimpleAdd.java:200)
at SimpleAddTest.SimpleAdd.jj_consume_token(SimpleAdd.java:138)
at SimpleAddTest.SimpleAdd.num(SimpleAdd.java:16)
at SimpleAddTest.SimpleAdd.expr(SimpleAdd.java:7)
at SimpleAddTest.Main.main(Main.java:9)
任何的提示來解決問題呢?
我修改了jj文件並使用了你的答案,但我得到了同樣的錯誤 – user203788
你確定你修改了return語句嗎?你重新運行JavaCC並重新編譯Java? –
是的,我做到了,這是一個github的文件回購,https://github.com/noorbakerally/SimpleAddJavaCC – user203788