Linker error when trying to use std::bitset

Question

Hi.

I have this code:

// Osman Zakir  
// 11 / 10 / 2021  
// Beginning C++20: From Novice to Professional by Ivor Horton and Peter Van Weert  
// Chapter 4 Exercise 7  
// Exercise Specs:  
/**  
 * Implement a program that prompts for the input of a letter. Use a library function  
 * to determine whether the letter is a vowel and whether it is lowercase or not, and output the  
 * result. Finally, output the lowercase letter together with its character code as a binary value. As  
 * a bonus exercise, you could try to do the latter without the use of std::format()?  
 */  
  
import <iostream>;  
import <bitset>;  
#include <cctype>  
  
int main()  
{  
    std::cout << "Enter a letter: ";  
    char letter{};  
    std::cin >> letter;  
    std::cin.ignore(32767, '\n');  
  
    const std::bitset<8> binary_letter{ static_cast<std::uint16_t>(std::tolower(letter)) };  
    if (std::isalpha(letter))  
    {  
        if (std::tolower(letter) == 'a' || std::tolower(letter) == 'e' ||  
            std::tolower(letter) == 'i' || std::tolower(letter) == 'o' ||  
            std::tolower(letter) == 'u')  
        {  
            std::cout << "Your letter is a vowel." << std::endl;  
            if (std::islower(letter))  
            {  
                std::cout << "It's lowercase, and in binary, it's " << binary_letter << std::endl;  
            }  
        }  
        else  
        {  
            std::cout << "Your letter is a consonant." << std::endl;  
            if (std::islower(letter))  
            {  
                std::cout << "It's lowercase, and in binary, it's " << binary_letter << std::endl;  
            }  
        }  
    }  
}  

I'm getting this linker error from it:

error LNK2019: unresolved external symbol "class std::ctype<char> const & __cdecl std::use_facet<class std::ctype<char> >(class std::locale const &)" (??$use_facet@V?$ctype@D@std@@@std@@YAABV?$ctype@D@0@ABVlocale@0@@Z) referenced >in function "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl std::operator<<<char,struct >std::char_traits<char>,8>(class std::basic_ostream<char,struct std::char_traits<char> > &,class std::bitset<8> const &)" (??$?>6DU?$char_traits@D@std@@$07@std@@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@0@AAV10@Abv ?>$bitset@$07@0@@Z)
1>E:\programming\visual_studio_2019\Projects\beginningcpp20\chapter4ex7\Debug\chapter4ex7.exe : fatal error LNK1120: 1 >unresolved externals
1>Done building project "chapter4ex7.vcxproj" -- FAILED.

Trying to build it on godbolt shows that it should build, but I've already tried restarting VS2019 and cleaning and rebuilding it with no luck.

Answer 1

Setting "Translate Includes to Imports" to Yes also allowed the posted code to build successfully.

Answer 2

In addition to my previous suggestions, adding #include for locale header will also enable successful build -

import <bitset>;
import <iostream>;
#include <locale>
#include <cctype>

Answer 3

Hi @Osman Zakir ,

The program can run when I replace import <iostream>;import <bitset>; with #include<iostream> #include<bitset>, I suggest you try this method.

Best regards,

Elya

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