O（mn）和O（mnlgn）(O(mn) and O(mnlgn))

 罗杰 
 
 这是一个有效的，经过测试的用例语法。 我尝试使用你所拥有的但它失败并且看起来不完整。 以下是两个示例，用于演示条件存在时的可选外观： 
 
S = A <space> B [<space> optC]

A = "a"

B = "b"

C = "c"

optC = C

space = #' '
 
 以下是两个输出： 
 
;input 1 = "a b"
;produces

=> [:S [:A "a"] [:B "b"]]

input 2 = "a b c"
;produces

=> [:S [:A "a"] [:B "b"] [:optC [:C "c"]]]
 
 用你的语法。 正如我所说，我遇到了麻烦，因为它似乎没有完全定义，但一般来说： 
 
(* If you change this *)

interface = <interface_dec> uses

(* to this, you should get similar results *)

interface = <interface_dec> [uses] 
 
 如果这不起作用，那么您需要提供一个语法，该语法与提供的输入样本一起使用，因为它们似乎不同步。 

Roger
 
Here is a valid, tested use case grammar. I tried using what you have but it is failing and doesn't appear complete. Following this are two examples to demonstrate optional appearance if condition exists:
 
S = A <space> B [<space> optC]

A = "a"

B = "b"

C = "c"

optC = C

space = #' '
 
Here are the two outputs:
 
;input 1 = "a b"
;produces

=> [:S [:A "a"] [:B "b"]]

input 2 = "a b c"
;produces

=> [:S [:A "a"] [:B "b"] [:optC [:C "c"]]]
 
With your grammar. As I said, I was having trouble as it does not appear fully defined but generally speaking:
 
(* If you change this *)

interface = <interface_dec> uses

(* to this, you should get similar results *)

interface = <interface_dec> [uses] 
 
If that doesn't work then you would need to provide a grammar that works with the input sample provided as they seem out of synch.