one bitset simple question

[Hunter Hou]

Hello,

I have this very simple program, but it can't be compiled. What's wrong
here?

thanks,
hunter


#include <iostream>
#include <bitset>

int main()
{


std::bitset<6> b1("101010");

std::cout << b1 << std::endl;

return 0;

}


The error is:
bitset.cpp: In function `int main()':
bitset.cpp:8: invalid conversion from `const char*' to `long unsigned int'
bitset.cpp:8: initializing argument 1 of `std::bitset<_Nb>::bitset(long
unsigned int) [with unsigned int _Nb = 6]'


Compiler says can't convert, but bitset<> has such an explicit constructor.

P.S. > If I use default constructor, everything is fine.

 

[Bill Seurer]

std::bitset<6> b1("101010");

Try:
std::bitset<6> b1(string("101010"));

 

[P.J. Plauger]

std::bitset<6> b1("101010");

std::cout << b1 << std::endl;

return 0;

}


The error is:
bitset.cpp: In function `int main()':
bitset.cpp:8: invalid conversion from `const char*' to `long unsigned int'
bitset.cpp:8: initializing argument 1 of `std::bitset<_Nb>::bitset(long
unsigned int) [with unsigned int _Nb = 6]'


Compiler says can't convert, but bitset<> has such an explicit

constructor.

No it doesn't. It has a template constructor that takes a string.
Try:

std::bitset<6> b1(string("101010"));

P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com

 

[Kai-Uwe Bux]

#include <iostream>
#include <bitset>

int main()
{


std::bitset<6> b1("101010");

std::cout << b1 << std::endl;

return 0;

}

Try

#include <iostream>
#include <bitset>
#include <string>

int main()
{


std::bitset<6> b1( std::string( "101010" ) );

std::cout << b1 << std::endl;

return 0;

}


Best

Kai-Uwe Bux

 

[SaltPeter]

Hello,

I have this very simple program, but it can't be compiled. What's wrong
here?

thanks,
hunter


#include <iostream>
#include <bitset>

int main()
{


std::bitset<6> b1("101010");

std::cout << b1 << std::endl;

return 0;

}


The error is:
bitset.cpp: In function `int main()':
bitset.cpp:8: invalid conversion from `const char*' to `long unsigned int'
bitset.cpp:8: initializing argument 1 of `std::bitset<_Nb>::bitset(long
unsigned int) [with unsigned int _Nb = 6]'


Compiler says can't convert, but bitset<> has such an explicit constructor.

P.S. > If I use default constructor, everything is fine.

Your compiler is confused, clarify your intentions by first locating the
bitset constructor, if any, that takes a string or char* literal. Its trying
to initialize the bitset container with an unsigned long integer. You could
declare a std::bitset<8> and initialize it with 0x2A or 42 for a binary
sequence of 00101010.

But fortunately, you shouldn't need to, bitset takes a reference to a
std::string as an arguement to one of its constructors:
in <bitset>.... you will find something like this:

explicit bitset(const string& _S, size_t _P = 0, size_t _L = (size_t)(-1))

so try declaring a std::string and initializing it with "101010".

#include <iostream>
#include <bitset>

int main()
{
std::string s1("101010");
std::bitset<6> b1(s1);

std::cout << b1 << std::endl;

return 0;
}

Also:

#include <iostream>
#include <bitset>

int main()
{
std::bitset<8> b1(0x2A); // 00101010

int sz = b1.size();
for (int i = 0; i < sz; i++) // from b1[7] to b1[0]
{
std::cout << b1[sz - i - 1];
}

std::cout << std::endl;

return 0;
}

 

[Hunter Hou]

Your compiler is confused, clarify your intentions by first locating the
bitset constructor, if any, that takes a string or char* literal. Its trying
to initialize the bitset container with an unsigned long integer. You could
declare a std::bitset<8> and initialize it with 0x2A or 42 for a binary
sequence of 00101010.

But fortunately, you shouldn't need to, bitset takes a reference to a
std::string as an arguement to one of its constructors:
in <bitset>.... you will find something like this:

explicit bitset(const string& _S, size_t _P = 0, size_t _L = (size_t)(-1))
Exactly.


so try declaring a std::string and initializing it with "101010".

#include <iostream>
#include <bitset>

int main()
{
std::string s1("101010");
std::bitset<6> b1(s1);

std::cout << b1 << std::endl;

return 0;
}

since string can be defined by const char*, why I have to use a string?
because it's explicit?

 

[SaltPeter]

(size_t)(-1))

since string can be defined by const char*, why I have to use a string?
because it's explicit?

Thats correct, an implicit conversion is not allowed. Its true for a
templated constructor as well since a templated cstor implies the explicit
keyword.

You may find section 9.4 in the following URL usefull:
http://www.icce.rug.nl/documents/cplusplus/cplusplus09.html#l142