字符串分割
turbo::str_split() 分割字符串
turbo::str_split() 函数提供了一种将字符串拆分为子字符串的简单方法。
str_split() 接受一个要分割的输入字符串、一个用于分割字符串的分隔符（例如逗号 ,），
以及（可选）一个谓词，用于充当过滤器来判断分割元素是否包含在结果集。 str_split() 还将返 回的集合调整为调用者指定的类型。
示例：
// Splits the given string on commas. Returns the results in a
// vector of strings. (Data is copied once.)
std::vector<std::string> v = turbo::str_split("a,b,c", ','); // Can also use ","
// v[0] == "a", v[1] == "b", v[2] == "c"
// Splits the string as in the previous example, except that the results
// are returned as `std::string_view` objects, avoiding copies. Note that
// because we are storing the results within `std::string_view` objects, we
// have to ensure that the input string outlives any results.
std::vector<std::string_view> v = turbo::str_split("a,b,c", ',');
// v[0] == "a", v[1] == "b", v[2] == "c"
str_split() 使用传递的 Delimiter 对象分割字符串。（请参阅下面的 Delimiters。）但是，在许多情况下，
您可以简单地传递字符串文字作为分隔符（它将隐式转换为 turbo::ByString 分隔符）。
示例：
// By default, empty strings are *included* in the output. See the
// `turbo::SkipEmpty()` predicate below to omit them{#stringSplitting}.
std::vector<std::string> v = turbo::str_split("a,b,,c", ',');
// v[0] == "a", v[1] == "b", v[2] == "", v[3] = "c"
// You can also split an empty string
v = turbo::str_split("", ',');
// v[0] = ""
// The delimiter need not be a single character
std::vector<std::string> v = turbo::str_split("aCOMMAbCOMMAc", "COMMA");
// v[0] == "a", v[1] == "b", v[2] == "c"
// You can also use the empty string as the delimiter, which will split
// a string into its constituent characters.
std::vector<std::string> v = turbo::str_split("abcd", "");
// v[0] == "a", v[1] == "b", v[2] == "c", v[3] = "d"
适应返回类型
str_split() API 更有用的功能之一是它能够将其结果集调整为所需的返回类型。 str_split()
返回的集合可能包含 std::string、std::string_view 或任何可以从 std::string_view
显式创建的对象。此模式适用于所有标准 STL 容器，包括 std::vector、std::list、std::deque、std::set、std::multiset、
std::map ，和std::multimap，甚至std::pair，它实际上不是一个容器。
示例：
// Stores results in a std::set<std::string>, which also performs de-duplication
// and orders the elements in ascending order.
std::set<std::string> s = turbo::str_split("b,a,c,a,b", ',');
// s[0] == "a", s[1] == "b", s[2] == "c"
// Stores results in a map. The map implementation assumes that the input
// is provided as a series of key/value pairs. For example, the 0th element
// resulting from the split will be stored as a key to the 1st element. If
// an odd number of elements are resolved, the last element is paired with
// a default-constructed value (e.g., empty string).
std::map<std::string, std::string> m = turbo::str_split("a,b,c", ',');
// m["a"] == "b", m["c"] == "" // last component value equals ""
// Stores first two split strings as the members in a std::pair. Any split
// strings beyond the first two are omitted because std::pair can hold only two
// elements.
std::pair<std::string, std::string> p = turbo::str_split("a,b,c", ',');
// p.first = "a", p.second = "b" ; "c" is omitted
分隔符
str_split() API 提供了许多“分隔符”来提供特殊的分隔符行为。 Delimiter 实现包含一个Find()函数，
该函数知道如何在给定的std::string_view中查找其自身的第一次出现。分隔符概念的模型表示特定类型的分隔符，
例如单个字符、子字符串，甚至正则表达式。
以下分隔符抽象作为“str_split()”的一部分提供应用程序编程接口：
turbo::ByString()(default forstd::stringarguments)turbo::ByChar()(default for acharargument)turbo::ByAnyChar()(for mixing delimiters)turbo::ByLength()(for applying a delimiter a set number of times)turbo::MaxSplits()(for splitting a specific number of times)
示例：
// Because a `string` literal is converted to an `turbo::ByString`, the following
// two splits are equivalent.
std::vector<std::string> v = turbo::str_split("a,b,c", ",");
std::vector<std::string> v = turbo::str_split("a,b,c", turbo::ByString(","));
// v[0] == "a", v[1] == "b", v[2] == "c"
// Because a `char` literal is converted to an `turbo::ByChar`, the following two
// splits are equivalent.
std::vector<std::string> v = turbo::str_split("a,b,c", ',');
// v[0] == "a", v[1] == "b", v[2] == "c"
std::vector<std::string> v = turbo::str_split("a,b,c", turbo::ByChar(','));
// v[0] == "a", v[1] == "b", v[2] == "c"
// Splits on any of the given characters ("," or ";")
vector<std::string> v = turbo::str_split("a,b;c", turbo::ByAnyChar(",;"));
// v[0] == "a", v[1] == "b", v[2] == "c"
// Uses the `turbo::MaxSplits` delimiter to limit the number of matches a
// delimiter can have. In this case, the delimiter of a literal comma is limited
// to matching at most one time. The last element in the returned collection
// will contain all unsplit pieces, which may contain instances of the
// delimiter.
std::vector<std::string> v = turbo::str_split("a,b,c", turbo::MaxSplits(',', 1));
// v[0] == "a", v[1] == "b,c"
// Splits into equal-length substrings.
std::vector<std::string> v = turbo::str_split("12345", turbo::ByLength(2));
// v[0] == "12", v[1] == "34", v[2] == "5"
过滤条件(谓词)
谓词可以通过确定结果元素是否包含在结果集中来过滤str_split()操作的结果。过滤谓词可以作为可选第三个参数传递给str_split()函数。
谓词必须是一元函数（或函数对象，例如 lambda），它采用单个 std::string_view 参数并返回 bool指示是否应包含参数（true）或排除参数（false）。
使用谓词很有用的一个例子是：过滤掉空子字符串。默认情况下，str_split()可以将空子字符串作为结果集中的单独元素返回，这类似于其他编程语言中 split 函数的工作方式。
// Empty strings *are* included in the returned collection.
std::vector<std::string> v = turbo::str_split(",a,,b,", ',');
// v[0] == "", v[1] == "a", v[2] == "", v[3] = "b", v[4] = ""
只需将提供的SkipEmpty()谓词作为第三个参数传递给str_split()函数，即可从结果集中过滤掉这些空字符串。 SkipEmpty() 不会将包含所有空格的字符串视为空。对于该行为，请使用SkipWhitespace()谓词。
示例：
// Uses turbo::SkipEmpty() to omit empty strings. Strings containing whitespace
// are not empty and are therefore not skipped.
std::vector<std::string> v = turbo::str_split(",a, ,b,", ',', turbo::SkipEmpty());
// v[0] == "a", v[1] == " ", v[2] == "b"
// Uses turbo::SkipWhitespace() to skip all strings that are either empty or
// contain only whitespace.
std::vector<std::string> v = turbo::str_split(",a, ,b,", ',',
turbo::SkipWhitespace());
// v[0] == "a", v[1] == "b"
// Passes a lambda as the predicate to keep only the lines that don't start
// with a `#`.
std::vector<std::string> non_comment_lines = turbo::str_split(
file_content, '\n',
[](std::string_view line) { return !turbo::StartsWith(line, "#"); });