jcon对expr的解析如 1+2*3+4/5

[acodercc]

    var jcon = require('jcon');
    var epsilon = jcon.string('');
    var num = jcon.regex(/\d+/).setAst('num');
    var sum_operator = jcon.regex(/[\+\-]/).setAst('operator');
    var product_operator = jcon.regex(/[\*\/]/).setAst('operator');
    var skips = jcon.regex(/\s*/).skip();
    var product = jcon.lazy(function(){
        return jcon.or(
            num,
            jcon.seq(num, product_rest)
        );
    }).setAst('product');
    var product_rest = jcon.or(epsilon, jcon.seq(skips, product_operator, skips, product));

    var sum = jcon.lazy(function(){
        return jcon.or(product,
            jcon.seq(product, sum_rest)
        );
    }).setAst('sum');
    var sum_rest = jcon.or(epsilon, jcon.seq(skips, sum_operator, skips, sum));

    var s = sum.parse('1+2*3+4/5').ast();
    console.log(JSON.stringify(s, null, '  '));

[acodercc]

sum和product的ast设置错误，应该设置在seq rest的节点上，lazy只是为了在rest定义前使用rest定义sum或product