working with bitsets some advice please

[Dk786]

hi ok so i have this scenario:

i have a bitset;

e.g.

bitset<16> mybitset (string("10000000000000000"))

where all 16 spaces have been utilized;

for now i just want to use the first 4 elements i.e. 1000. i need a whole number 1000 and NOT individual numbers (1,0,0,0) at different index positions
I need a whole number so that i can compare it with other bitsets which already only have 4 elemets. i.e.

bitset<4> stop (string("0000")); if(stop== mybitset) { //do something }

how do i go about implementing this? kinda new to bitsets
thanks!!
P.S. im working with binary numbers!

[Bourgond Aries]

You could create a function that starts with a

int start = 0;

For every zero, you time start by 10. For every 1 you add 1 AND time by 10:

int start = 0;
for (int i = 0; i < 4; ++i)
{
    start *= 10;
    start += (mybitset[i] ? 1 : 0);
}

[Dk786]

thanks for your reply! i must be doing something wrong since the value of start ends up to 0 instead of 1000, i dont have any idea why that happens

[Bourgond Aries]

Bitset is reversing the string that you store. You're not doing anything wrong I think. Try using the flip() function before reading :)

[JLBorges]

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

int main()
{
    const std::bitset<16> mybitset( std::string( "10000000000000000") ) ;
    const std::bitset<4> stop( std::string( "1000") ) ;

    if( mybitset.to_string().find( stop.to_string() ) == 0 )
        std::cout << "//do something\n" ; // do something

    // or
    if( ( mybitset >> 12 ).to_ulong() == stop.to_ulong() )
        std::cout << "//do something\n" ; // do something
}

http://liveworkspace.org/code/xZ21O$0

[Dk786]

flipping doesn't work, if i flip the value is 1111 :(

[Bourgond Aries]

 Why not perform the iteration backwards?
 Start at the highest element, --i?

[Dk786]

@JLBorges thanks for your solution, after i modified it a little it works! thanks and thank you also @Bourgond Aries for all your help!

Thanks again :)