dropincc.java 是
- 一个简单、好用的语法解析器生成器；
- 专为java语言环境下，实施DSL方案而设计；
- 特点：使用纯java语法(Fluent Interface)制定用户的词法、语法规则；jdk1.6 compiler API动态编译为字节码；自动管理字节码、用户无需关心具体生成的解析器源码；专为DSL打造，相对与使用其它常见工具(javacc, antlr等)做DSL解析，代码量急剧下降；上手较为容易，让用户更加关注自身业务内容
- 需要jdk1.6或以上版本运行,无任何其它依赖
- 识别LL(*)语法
/**
* EBNF of Calculator:
* <pre>
* calc ::= expr $
* expr ::= addend (('+'|'-') addend)*
* addend ::= factor (('*'|'/') factor)*
* factor ::= '(' expr ')'
* | '\\d+(\\.\\d+)?'
* </pre>
*/
public static void main(String... args) throws Throwable {
Lang c = new Lang("Calculator");
Grule expr = c.newGrule();
c.defineGrule(expr, CC.EOF).action(new Action() {
public Double act(Object matched) {
return (Double) ((Object[]) matched)[0];
}
});
TokenDef a = c.newToken("\\+");
Grule addend = c.newGrule();
expr.define(addend, CC.ks(a.or("\\-"), addend)).action(new Action() {
public Double act(Object matched) {
Object[] ms = (Object[]) matched;
Double a0 = (Double) ms[0];
Object[] aPairs = (Object[]) ms[1];
for (Object p : aPairs) {
String op = (String) ((Object[]) p)[0];
Double a = (Double) ((Object[]) p)[1];
if ("+".equals(op)) {
a0 += a;
} else {
a0 -= a;
}
}
return a0;
}
});
TokenDef m = c.newToken("\\*");
Grule factor = c.newGrule();
addend.define(factor, CC.ks(m.or("/"), factor)).action(new Action() {
public Double act(Object matched) {
Object[] ms = (Object[]) matched;
Double f0 = (Double) ms[0];
Object[] fPairs = (Object[]) ms[1];
for (Object p : fPairs) {
String op = (String) ((Object[]) p)[0];
Double f = (Double) ((Object[]) p)[1];
if ("*".equals(op)) {
f0 *= f;
} else {
f0 /= f;
}
}
return f0;
}
});
factor.define("\\(", expr, "\\)").action(new Action() {
public Double act(Object matched) {
return (Double) ((Object[]) matched)[1];
}
}).alt("\\d+(\\.\\d+)?").action(new Action() {
public Double act(Object matched) {
return Double.parseDouble((String) matched);
}
});
Exe exe = c.compile();
System.out.println(exe.eval("1 +2+3+(4 +5*6*7*(64/8/2/(2/1 )/1)*8 +9 )+ 10"));
}