[英]How to simplify JavaScript/ECMAScript array literal production?
I currently implementing a JavaScript/ ECMAScript 5.1 parser with JavaCC and have problems with the ArrayLiteral production. 我目前使用JavaCC实现JavaScript / ECMAScript 5.1解析器,并且ArrayLiteral生产遇到问题。
ArrayLiteral :
[ Elision_opt ]
[ ElementList ]
[ ElementList , Elision_opt ]
ElementList :
Elision_opt AssignmentExpression
ElementList , Elision_opt AssignmentExpression
Elision :
,
Elision ,
I have three questions, I'll ask them one by one. 我有三个问题,我会一一问。
I have tried to simplify/to rewrite the ArrayLiteral
production depicted above and finally arrived to the following production (pseudo-grammar): 我试图简化/重写上面描述的
ArrayLiteral
生产,并最终到达以下生产(伪语法):
ArrayLiteral:
"[" ("," | AssignmentExpression ",") * AssignmentExpression ? "]"
My first question: is this rewriting correct? 我的第一个问题:这次重写正确吗?
Two other quetsions: 其他两个问题:
Yes, that correctly captures the grammar presented. 是的,可以正确捕获所呈现的语法。
However, a better rewrite would be: 但是,更好的重写方法是:
"[" AssignmentExpression ? ( "," AssignmentExpression ? ) * "]"
because the rewriting in the OP is not LL(1) -- you cannot distinguish the possibilities without reading the entire AssignmentExpression
-- whereas with this one you can figure out which alternative to use simply by looking at the first token. 因为在OP中的重写不是LL(1)-您无法在不阅读整个
AssignmentExpression
情况下区分各种可能性-而通过此重写,您可以通过查看第一个令牌来找出使用哪种替代方案。
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