是否有可能在cin上使用std操纵器忽略punctuacion?例如,假设您有一个输入流(在实际情况下是一个文件),如:“一,二三”。我希望能够做到:
f >> ignore_punct >> a;
f >> ignore_punct >> b;
f >> ignore_punct >> c;
最后a=="one"
,b=="two"
,c=="three"
。
答案 0 :(得分:1)
没有标准库的方法,但如果我理解正确的话,这很容易做到。如果你想读一个字符串直到一些标点符号就好像是换行符一样,那么你可以使用一个getline
版本接受一个谓词而不是一个分隔符:
template<class F>
std::istream& getline(std::istream& stream, std::string& string, F delim) {
string.clear();
// Get characters while the stream is valid and the next character is not the terminating delimiter.
while (stream && !delim(stream.peek()))
string += stream.get();
// Discard delimiter.
stream.ignore(1);
return stream;
};
用法示例:
#include <iostream>
#include <cctype>
int main(int argc, char** argv) {
std::string s;
getline(std::cin, s, ::ispunct);
std::cout << s << '\n';
return 0;
}
如果您还希望打破换行符,那么您可以编写一个仿函数:
struct punct_or_newline {
bool operator()(char c) const { return ::ispunct(c) || c == '\n'; }
};
然后调用getline(std::cin, my_string, punct_or_newline())
。希望这有帮助!
答案 1 :(得分:1)
试试这个:
它使用local来过滤掉标点符号 这允许其余代码保持不变。
#include <locale>
#include <string>
#include <iostream>
#include <fstream>
#include <cctype>
class PunctRemove: public std::codecvt<char,char,std::char_traits<char>::state_type>
{
bool do_always_noconv() const throw() { return false;}
int do_encoding() const throw() { return true; }
typedef std::codecvt<char,char,std::char_traits<char>::state_type> MyType;
typedef MyType::state_type state_type;
typedef MyType::result result;
virtual result do_in(state_type& s,
const char* from,const char* from_end,const char*& from_next,
char* to, char* to_limit, char*& to_next ) const
{
/*
* This function is used to filter the input
*/
for(from_next = from, to_next = to;from_next != from_end;++from_next)
{
if (!std::ispunct(*from_next))
{
*to_next = *from_from;
++to_next;
}
}
return ok;
}
/*
* This function is used to filter the output
*/
virtual result do_out(state_type& state,
const char* from, const char* from_end, const char*& from_next,
char* to, char* to_limit, char*& to_next ) const
{ /* I think you can guess this */ }
};
int main()
{
// stream must be imbued before they are opened.
// Otherwise the imbing is ignored.
//
std::ifstream data;
data.imbue(std::locale(std::locale(), new PunctRemove));
data.open("plop");
if (!data)
{
std::cout << "Failed to open plop\n";
return 1;
}
std::string line;
std::getline(data, line);
std::cout << "L(" << line << ")\n";
}