骰子表示法（递归下降解析实现）：没有分隔符的扫描器

发布于 2024-10-14 08:35:50 字数 1203 浏览 1 评论 0原文

如果可能的话，我想使用 java Scanner 构建骰子符号的递归下降解析实现。我之前曾提出过有关它的问题，但我的要求似乎过于简单化了。所以我在这里提出这个全球性的请求。

我真的希望这对于 java.util.Scanner 类是可行的，但如果需要，我将编写自己的扫描仪。我现在想避免这种情况。

 expression   =  { whitespace } , [ plusminus ] , roll , { plusminus , ( roll | number , { whitespace } ) } ;
 roll         =  [ number ] , ( "d" | "D" ) , ( number | "%") , [ "-" ( "L" | "H" ) ] , { whitespace } ;
 plusminus    =  ( "+" | "-" ) , { whitespace } ;
 number       =  nonzerodigit , { digit } ;
 digit        =  nonzero digit | "0" ;
 nonzerodigit =  "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
 whitespace   =  ? Java definition of a whitespace ? ;

所以事实上，我尝试编写以下代码：

 Scanner s = new Scanner("1d6");
 if (s.hasNextInt()) {
  s.nextInt();
 } else {
  throw new java.text.ParseException();
 }

但显然它一直失败。

另外，正如上一个问题中所建议的，我尝试了 findWithinHorizon 方法，但它确实找到了下一个模式，并且不会从我所在的位置进行检查。因此，如果不是我需要的字符串，我就无法“推回”该字符串...

因此，关于如何在这种情况下使用 java.util.Scanner 有什么建议吗？或者也许我必须编写自己的扫描仪？

原文

I would like to build a recursive descent parsing implementation of the dice notation using the java Scanner if possible. I've previously opened a question about it , but it seemed that I had my requirements way too simplified. So I'm presenting here the request in its globality.

I really hope that this is feasible with the class java.util.Scanner, but if needed I will write my own scanner. I would like to avoid this one right now.

 expression   =  { whitespace } , [ plusminus ] , roll , { plusminus , ( roll | number , { whitespace } ) } ;
 roll         =  [ number ] , ( "d" | "D" ) , ( number | "%") , [ "-" ( "L" | "H" ) ] , { whitespace } ;
 plusminus    =  ( "+" | "-" ) , { whitespace } ;
 number       =  nonzerodigit , { digit } ;
 digit        =  nonzero digit | "0" ;
 nonzerodigit =  "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
 whitespace   =  ? Java definition of a whitespace ? ;

So in fact, I've tried to write the following code:

 Scanner s = new Scanner("1d6");
 if (s.hasNextInt()) {
  s.nextInt();
 } else {
  throw new java.text.ParseException();
 }

But obviously it keeps failing.

Also as suggested in the previous question, I've tried the findWithinHorizon methods but it really finds the next pattern and doesn't check from where I am. So I can't "pushback" the string if it is not what I need...

So any suggestion on how I should use java.util.Scanner in this context? Or maybe I have to write my own scanner?

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