DSL語法解析器生成器：dropincc.java

dropincc.java 是

• 一個簡單、好用的語法解析器生成器；
• 專為java語言環境下，實施DSL方案而設計；
• 特點：使用純java語法(Fluent Interface)制定用戶的詞法、語法規則；jdk1.6 compiler API動態編譯為字節碼；自動管理字節碼、用戶無需關心具體生成的解析器源碼；專為DSL打造，相對與使用其它常見工具(javacc, antlr等)做DSL解析，代碼量急劇下降；上手較為容易，讓用戶更加關注自身業務內容
• 需要jdk1.6或以上版本運行,無任何其它依賴
• 識別LL(*)語法

/**
 * 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"));
}

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