Boost String Algorithms Library 函数详解三 (find)

Table 11.4. Find algorithms

Algorithm name	Description	Functions
find_first	Find the first occurrence of a string in the input	find_first() ifind_first()
find_last	Find the last occurrence of a string in the input	find_last() ifind_last()
find_nth	Find the nth (zero-indexed) occurrence of a string in the input	find_nth() ifind_nth()
find_head	Retrieve the head of a string	find_head()
find_tail	Retrieve the tail of a string	find_tail()
find_token	Find first matching token in the string	find_token()
find_regex	Use the regular expression to search the string	find_regex()
find	Generic find algorithm	find()

基础示例：

 string str1("a1234_first_nth_first_nth_");
 boost::iterator_range<string::iterator> ir;
 
 // find_first 
 // ifind_first -- 不区分大小写，其它同find_first
 ir = find_first(str1, "first");
 assert(string(ir.begin(), ir.end()) == "first"); // 比较字符串
 assert(ir.begin() - str1.begin() == 6 && ir.end()-str1.begin() == 6 + 5); //查看搜索到的字符串所在位置
 to_upper(ir); // 利用iterator_range处理搜索到的字符串
 assert(str1 == "a1234_FIRST_nth_first_nth_");
 to_lower(ir);
 assert(str1 == "a1234_first_nth_first_nth_");
 ir = find_first(str1, "no");
 assert(ir.empty()); // 不存在
 assert(string(ir.begin(), ir.end()).empty()); // 不存在，仍可构建一个string
 ostringstream osstr;
     osstr << find_first( str1, "_first_" );
     assert( osstr.str()=="_first_" );
 
 // find_last -- 同findfirst，只是方向相反
 // ifind_last -- 不区分大小写，其它同findlast

 // find_nth
 ir = find_nth(str1, "nth", 1);
 assert(ir.begin() - str1.begin() == 22);
 ir = find_nth(str1, "nth", 0);
 assert(ir.begin() - str1.begin() == 12);
 // find_head
 // find_tail只是方向相反
 ir = find_head(str1, 5);
 transform(ir.begin(), ir.end(), ir.begin(), bind2nd(plus<char>(), 1));
 assert(str1 == "b2345_first_nth_first_nth_");
 // find_token
 ir = find_token(str1, is_any_of("irfst"));
 assert(string(ir.begin(), ir.end()) == "f");
 ir = find_token(str1, is_any_of("xfirts"), token_compress_off );
 assert(string(ir.begin(), ir.end()) == "f");
 ir = find_token(str1, is_any_of("irfst"), token_compress_on );
 assert(string(ir.begin(), ir.end()) == "first");
 ir = find_token(str1, is_any_of("fitr "), token_compress_on );
 assert(string(ir.begin(), ir.end()) == "fir");
 // find_regex
 boost::regex rx("b[0-9]+_");
 ir = find_regex(str1, rx);
 assert(string(ir.begin(), ir.end()) == "b2345_");
 // find_all_regex test table 11.4 里没有列出，boost_1_33_0\libs\algorithm\string\test 目录下有
 string str2("b1_b22_b333_b4444");
 vector<string> tokens;
     find_all_regex(tokens, str2, rx);
 assert(tokens.size() == 3);
 assert(tokens[0] == "b1_");
 assert(tokens[1] == "b22_");
 assert(tokens[2] == "b333_");
 // find
 ir = find(str1, first_finder(string("b2345_")));
 assert(string(ir.begin(), ir.end()) == "b2345_");;