Remove/replace Multicharacters (ÿû) in a C++ String

Question

I am trying to replace the multicharacters in a string using std::tr1::regex as I am not able to find any function that can help to replace them. The code is as below:

// Example program
#include <iostream>
#include <string>
#include <tr1/regex>

void f1()
{
 std::string str = "ÿûABC";
 std::tr1::regex rx("ÿû");
 std::string replacement = "";
 std::tr1::regex_replace(str,rx,replacement);
}

int main()
{
  f1();
  return 0;
}

But I am receiving the below compilation error. Could anyone please suggest if there is any to resolve it or any better option to replace them using C++98?

In file included from 4:0:
/usr/include/c++/4.9/tr1/regex:2407:5: warning: inline function '_Out_iter std::tr1::regex_replace(_Out_iter, _Bi_iter, _Bi_iter, const std::tr1::basic_regex&, const std::basic_string&, std::tr1::regex_constants::match_flag_type) [with _Out_iter = std::back_insert_iterator >; _Bi_iter = __gnu_cxx::__normal_iterator >; _Rx_traits = std::tr1::regex_traits; _Ch_type = char; std::tr1::regex_constants::match_flag_type = std::bitset]' used but never defined
     regex_replace(_Out_iter __out, _Bi_iter __first, _Bi_iter __last,
     ^
/tmp/ccGJXgKd.o: In function `f1()':
:(.text+0x81): undefined reference to `std::tr1::basic_regex >::_M_compile()'
:(.text+0xc5): undefined reference to `std::back_insert_iterator std::tr1::regex_replace, __gnu_cxx::__normal_iterator, std::tr1::regex_traits, char>(std::back_insert_iterator, __gnu_cxx::__normal_iterator, __gnu_cxx::__normal_iterator, std::tr1::basic_regex > const&, std::basic_string, std::allocator > const&, std::bitset)'
collect2: error: ld returned 1 exit status

How about plain [`std::string::replace`](https://en.cppreference.com/w/cpp/string/basic_string/replace)? Or, considering your replacement, [`std::string::erase`](https://en.cppreference.com/w/cpp/string/basic_string/erase)? Don't complicate things, and regular expressions almost universally complicates things. — Some programmer dude, Feb 04 '20 at 08:09
`tr1` is not part of `C++98`. Anyhow, why would you program in an obsolete C++ dialect? — Ulrich Eckhardt, Feb 04 '20 at 08:12
You're pretty much shot in the foot already because the encoding of those characters in your source code is *locale-specific*. Use `U""`, `u""`, or `u8""` to ensure Unicode. And have a look at [ICU](http://site.icu-project.org/) until the C++ standard comes up with full Unicode capabilities (C++23 or somesuch, I have not given up hope...) — DevSolar, Feb 04 '20 at 08:13
gcc 4.9 has decent c++11 support. Why tie a hand behind your back by using experimental additions to C++98? This isn't intended to nag or as an insult; if you have a reason, I'm interested in knowing what it is. — user4581301, Feb 04 '20 at 08:14
There is an urgent necessity to resolve it in C++98 as of now. — Vijaykumar Ainapur, Feb 04 '20 at 08:26

score 1 · Accepted Answer · answered Feb 04 '20 at 08:46

To erase a sub-string from another string, you should use the erase function.

Example:

#include<iostream>
#include<string>

int main()
{
    std::string str = "ÿûABC";
    std::string remove = "ÿû";

    std::cout << "Length of source string is " << str.length() << " characters\n";
    std::cout << "Length of string to remove is " << remove.length() << " characters\n";

    size_t pos = str.find(remove);
    if (pos == std::string::npos)
    {
        std::cout << "Substring \"ÿû\" not found\n";
    }
    else
    {
        std::cout << "Found sub-string \"" << remove << "\" at position " << pos << '\n';
        str.erase(pos, remove.length());
        std::cout << "After erasing: \"" << str << "\"\n";
    }
}

Output from working example:

Length of source string is 7 characters
Length of string to remove is 4 characters
Found sub-string "ÿû" at position 0
After erasing: "ABC"

The important parts to note here is that the characters 'ÿ' and 'û' are not single bytes! Your editor probably saved them as two-bytes each, encoded with UTF-8.

By putting the sub-string to remove in its own std::string object, we can easily get the actual length of them for the erase call.

Remove/replace Multicharacters (ÿû) in a C++ String

1 Answers1