问题描述
假设我想分析一个带有各种开放和关闭括号的字符串（我在标题中使用了括号，因为我相信它更常见 - 但问题仍然相同），以便我将所有更高级别的字符分隔开一个列表。鉴于：
[hello：= [notting ]，[hill]] [3.4（4.56676 | 5.67787）] [hill [is [high]]不是]]
我想：
列表（[hello：= [notting]，[hill]] [3.4（4.56676 | 5.67787）]，[[hill [is [high]] not]]）
我这样做的方式是通过计算开始和结束括号并在我的计数器为0时添加到列表中。但是，我有一个难看的命令代码。您可能会认为原始字符串格式正确。
我的问题是：对这个问题有什么好的功能方法？
注意：我曾想过使用for ... yield构造，但考虑到使用计数器，我无法获得一个简单的条件（我必须有条件才能更新计数器），而且我也没有知道如何在这种情况下使用这个构造。
使用Scala解析器组合器库的快速解决方案：
import util.parsing.combinator.RegexParsers
对象Parser extends RegexParsers {
lazy val t =[^ \\\ [\\] \\\（\\）] +。r
def paren：Parser [String] =
（（〜〜 rep1（t | paren）〜）|
[〜〜rep1（t | paren）〜]）^^ {
case o〜l〜c => （o :: l ::: c :: Nil）mkString
}
def all = rep（paren）
def apply（s：String ）= parseAll（all，s）
}
在REPL中检查它：
scala>解析器（[hello：= [notting]，[hill]] [3.4（4.56676 | 5.67787）] [hill [is [high]]]）
res0：Parser.ParseResult [List [ String []] = [1.72] parsed：List（[hello：= [notting]，[hill]]，[3.4（4.56676 | 5.67787）] [[hill [is [high]]]）
Let's say I want to parse a string with various opening and closing brackets (I used parentheses in the title because I believe it is more common -- the question is the same nevertheless) so that I get all the higher levels separated in a list.
Given:
[hello:=[notting],[hill]][3.4(4.56676|5.67787)][the[hill[is[high]]not]]
I want:
List("[hello:=[notting],[hill]]", "[3.4(4.56676|5.67787)]", "[the[hill[is[high]]not]]")
The way I am doing this is by counting the opening and closing brackets and adding to the list whenever I get my counter to 0. However, I have an ugly imperative code. You may assume that the original string is well formed.
My question is: what would be a nice functional approach to this problem?
Notes: I have thought of using the for...yield construct but given the use of the counters I cannot get a simple conditional (I must have conditionals just for updating the counters as well) and I do not know how I could use this construct in this case.
Quick solution using Scala parser combinator library:
import util.parsing.combinator.RegexParsers
object Parser extends RegexParsers {
lazy val t = "[^\\[\\]\\(\\)]+".r
def paren: Parser[String] =
("(" ~ rep1(t | paren) ~ ")" |
"[" ~ rep1(t | paren) ~ "]") ^^ {
case o ~ l ~ c => (o :: l ::: c :: Nil) mkString ""
}
def all = rep(paren)
def apply(s: String) = parseAll(all, s)
}
Checking it in REPL:
scala> Parser("[hello:=[notting],[hill]][3.4(4.56676|5.67787)][the[hill[is[high]]not]]")
res0: Parser.ParseResult[List[String]] = [1.72] parsed: List([hello:=[notting],[hill]], [3.4(4.56676|5.67787)], [the[hill[is[high]]not]])
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