问题描述
有一个简单的方法来确定语法是LL1，LR0，SLR1 ...只是从语法上查看，而不进行任何复杂的分析？
实例：要决定一个BNF语法是LL1，你必须首先计算第一和跟随集合 - 这在一些情况下可能非常耗时。
有人有一个想法如何做到这一点更快？
任何帮助真的会感激！
首先，您无法判断语言是否为检查语法的LL（1），您只能对语法本身发表声明。对于存在LL（1）语法的语言，完全有可能写出非LL（1）语法。
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您可以为语法编写一个解析器，并让程序首先计算，然后为您跟踪集合和其他属性。
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检查语法并寻找违反的语法各种语法类型的约束。例如：LL（1）允许正确但不是左递归，因此，包含左递归的语法不是LL（1）。 （对于其他语法属性，你将不得不花费一些高质量的时间与定义，因为我现在不记得任何东西在我的头顶部：）
Is there a simple way to determine wether a grammar is LL1, LR0, SLR1... just from looking on the grammar without doing any complex analysis?
For instance: To decide wether a BNF Grammar is LL1 you have to calculate First and Follow sets first - which can be very time consuming in some cases.
Has anybody got an idea how to do this faster?Any help would really be appreciated!
First off, a bit of pedantry. You cannot determine whether a language is LL(1) from inspecting a grammar for it, you can only make statements about the grammar itself. It is perfectly possible to write non-LL(1) grammars for languages for which an LL(1) grammar exists.
With that out of the way:
You could write a parser for the grammar and have a program calculate first and follow sets and other properties for you. After all, that's the big advantage of BNF grammars, they are machine comprehensible.
Inspect the grammar and look for violations of the constraints of various grammar types. For instance: LL(1) allows for right but not left recursion, thus, a grammar that contains left recursion is not LL(1). (For other grammar properties you're going to have to spend some quality time with the definitions, because I can't remember anything else off the top of my head right now :).
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