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C++ Discussion Thread
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Jan 20th, 2006

conversion to binary

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Hey!
I just wanted to know that if there is any builtin function in c++ that converts a decimal number into binary number??

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aminura

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Jan 20th, 2006

Re: conversion to binary

no, but Google is a good place to find out how to do it.

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Jan 20th, 2006

Re: conversion to binary

>any builtin function in c++ that converts a decimal number into binary number??
Maybe, depending on what you want to do with it. If all you want is a string, then the bitset<> class is ideal:

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <bitset>
#include <climits>
 
int main()
{
  int dec;
 
  std::cout<<"Enter a whole number: ";
 
  if ( std::cin>> dec )
    std::cout<< std::bitset<sizeof dec * CHAR_BIT> ( dec ) <<'\n';
}
#include <iostream>
#include <bitset>
#include <climits>

int main()
{
  int dec;

  std::cout<<"Enter a whole number: ";
  
  if ( std::cin>> dec )
    std::cout<< std::bitset<sizeof dec * CHAR_BIT> ( dec ) <<'\n';
}

If you want an actual arithmetic value rather than a string, it's only marginally more difficult:

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <bitset>
#include <sstream>
#include <climits>
 
int main()
{
  int dec;
 
  std::cout<<"Enter a whole number: ";
 
  if ( std::cin>> dec ) {
    std::istringstream iss ( std::bitset<sizeof dec * CHAR_BIT> ( dec ).to_string() );
    unsigned long bit_num;
 
    iss>> bit_num;
    std::cout<< bit_num <<'\n';
  }
}
#include <iostream>
#include <bitset>
#include <sstream>
#include <climits>

int main()
{
  int dec;

  std::cout<<"Enter a whole number: ";
  
  if ( std::cin>> dec ) {
    std::istringstream iss ( std::bitset<sizeof dec * CHAR_BIT> ( dec ).to_string() );
    unsigned long bit_num;

    iss>> bit_num;
    std::cout<< bit_num <<'\n';
  }
}

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Jan 20th, 2006

Re: conversion to binary

Ohhh! pretty neat

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Jan 21st, 2006

Re: conversion to binary

Thanks for the reply! I guess I would have to go through a tutorial of bitset classes to get an understanding of what it is and how it works..!

Quote ...

if ( std::cin>> dec )

I would like to know what does this actually mean or how does this 'if statement' work?

Thanks

aminura

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Re: conversion to binary

>how does this 'if statement' work?
It's just a combination of these two statements:

C++ Syntax (Toggle Plain Text)
std::cin>> dec;
if ( cin )
std::cin>> dec;
if ( cin )

Put simply, if ( cin ) says "Is the stream happy?". Since dec is an integer, if you typed a letter instead of a number, std::cin>>dec would fail with a conversion error, placing the stream in a failure state. Because the stream is in a failure state, if ( cin ) isn't true, so the body of the statement isn't executed. But if you type a valid integer, std::cin>>dec succeeds and doesn't set any failure flags, so if ( cin ) is true and the body of the statement is executed.

C++ has all kinds of shortcuts. One of them is being able to combine those two statements into one:

C++ Syntax (Toggle Plain Text)
if ( std::cin>> dec )
if ( std::cin>> dec )

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