我想创建一个词法分析器规则,它可以读取定义自己的分隔符的字符串文字(具体来说,是Oracle引号分隔的字符串):
q'!My string which can contain 'single quotes'!'
其中!
用作分隔符,但理论上可以是任何字符。
是否可以通过词法分析器规则执行此操作,而不会对给定的语言目标产生依赖性?
答案 0 :(得分:3)
是否可以通过词法分析器规则执行此操作,而不会对给定的语言目标产生依赖性?
不,这样的事情需要目标依赖代码。
万一你或其他人正在阅读这个Q& A想知道如何使用目标代码完成此操作,这是一个快速演示:
lexer grammar TLexer;
@members {
boolean ahead(String text) {
for (int i = 0; i < text.length(); i++) {
if (_input.LA(i + 1) != text.charAt(i)) {
return false;
}
}
return true;
}
}
TEXT
: [nN]? ( ['] ( [']['] | ~['] )* [']
| [qQ] ['] QUOTED_TEXT [']
)
;
// Skip everything other than TEXT tokens
OTHER
: . -> skip
;
fragment QUOTED_TEXT
: '[' ( {!ahead("]'")}? . )* ']'
| '{' ( {!ahead("}'")}? . )* '}'
| '<' ( {!ahead(">'")}? . )* '>'
| '(' ( {!ahead(")'")}? . )* ')'
| . ( {!ahead(getText().charAt(0) + "'")}? . )* .
;
可以在课堂上进行测试:
public class Main {
static void test(String input) {
TLexer lexer = new TLexer(new ANTLRInputStream(input));
CommonTokenStream tokenStream = new CommonTokenStream(lexer);
tokenStream.fill();
System.out.printf("input: `%s`\n", input);
for (Token token : tokenStream.getTokens()) {
if (token.getType() != TLexer.EOF) {
System.out.printf(" token: -> %s\n", token.getText());
}
}
System.out.println();
}
public static void main(String[] args) throws Exception {
test("foo q'!My string which can contain 'single quotes'!' bar");
test("foo q'(My string which can contain 'single quotes')' bar");
test("foo 'My string which can contain ''single quotes' bar");
}
}
将打印:
input: `foo q'!My string which can contain 'single quotes'!' bar`
token: -> q'!My string which can contain 'single quotes'!'
input: `foo q'(My string which can contain 'single quotes')' bar`
token: -> q'(My string which can contain 'single quotes')'
input: `foo 'My string which can contain ''single quotes' bar`
token: -> 'My string which can contain ''single quotes'
替代<{p>中的.
| . ( {!ahead(getText().charAt(0) + "'")}? . )* .
可能有点过于宽松,但可以通过将其替换为否定或常规字符集来进行调整。