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我需要一個用於我的java應用程序的解析器,因此我發現了JParsec庫並使用簡單的計算器語法瀏覽了他們網站上的教程。看來我應該能夠按照我計劃使用該庫的方式進行操作,因此開始創建原型,將示例計算器中的十進制文字解析爲非常簡單的標識符作爲字符串。我現在想要工作的唯一操作是'+',用於連接字符串,但我不斷收到錯誤消息。這裏是我的代碼:解析簡單字符串表達式中的JParsec錯誤
import org.codehaus.jparsec.OperatorTable;
import org.codehaus.jparsec.Parser;
import org.codehaus.jparsec.Parsers;
import org.codehaus.jparsec.Scanners;
import org.codehaus.jparsec.Terminals;
import org.codehaus.jparsec.Tokens.Fragment;
import org.codehaus.jparsec.functors.Binary;
import org.codehaus.jparsec.functors.Map;
public class Test
{
enum BinaryOperator implements Binary<String> {
PLUS {
public String map(String a, String b) {
return a + b;
}
}
}
static final Parser<Void> IGNORED = Scanners.WHITESPACES.skipMany();
static final Parser<String> TEXT = Terminals.Identifier.TOKENIZER.map(new Map<Fragment, String>() {
public String map(Fragment arg0) {
return arg0.text()+"NEWTOSEEIFITSWORKING";
}
});
private static final Terminals OPERATORS = Terminals.operators("+");
static final Parser<?> TOKENIZER = Parsers.or(Terminals.Identifier.TOKENIZER, OPERATORS.tokenizer());
static Parser<?> term(String... names) {
return OPERATORS.token(names);
}
static <T> Parser<T> op(String name, T value) {
return term(name).retn(value);
}
static Parser<String> textparser(Parser<String> atom) {
Parser<String> parser = new OperatorTable<String>().infixl(op("+", BinaryOperator.PLUS), 10).build(atom);
return parser;
}
public static final Parser<String> TEXTPARSER = textparser(TEXT).from(TOKENIZER, IGNORED);
public static void main(String[] args)
{
System.out.println(TEXTPARSER.parse("hello+world"));
}}
,這裏是錯誤我越來越:
Exception in thread "main" org.codehaus.jparsec.error.ParserException: Cannot scan characters on tokens.
line 1, column 1
at org.codehaus.jparsec.Parser.asParserException(Parser.java:591)
at org.codehaus.jparsec.Parser.run(Parser.java:600)
at org.codehaus.jparsec.MapParser.apply(MapParser.java:30)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.MapParser.apply(MapParser.java:30)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.BindNextParser.apply(BindNextParser.java:37)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.Sequence2Parser.apply(Sequence2Parser.java:32)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.ParserInternals.runNestedParser(ParserInternals.java:116)
at org.codehaus.jparsec.NestedParser.apply(NestedParser.java:32)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.Sequence2Parser.apply(Sequence2Parser.java:32)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
at org.codehaus.jparsec.Parsers.parse(Parsers.java:97)
at org.codehaus.jparsec.Parser.parse(Parser.java:535)
at org.codehaus.jparsec.Parser.parse(Parser.java:546)
at org.codehaus.jparsec.Parser.parse(Parser.java:551)
at Test.main(Test.java:52)
Caused by: java.lang.IllegalStateException: Cannot scan characters on tokens.
at org.codehaus.jparsec.ParserState.characters(ParserState.java:56)
at org.codehaus.jparsec.PatternScanner.apply(PatternScanner.java:36)
at org.codehaus.jparsec.ReturnSourceParser.apply(ReturnSourceParser.java:32)
at org.codehaus.jparsec.Parser.run(Parser.java:597)
... 18 more
任何想法,我做錯了嗎?任何幫助是極大的讚賞!