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Use stand-alone function in cout-statement

 
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Eric Lilja
Guest
PostPosted: Mon Dec 20, 2004 10:46 pm    Post subject: Use stand-alone function in cout-statement Reply with quote


Hi, I need a function that expects a const std::string& containing the
visual representation of a number in binary format. It should then output
this number in groups of four bits separated by a space. If the length of
the string is not divisable by four (normally, it should receive 8-bit
numbers (that is, strings of length Cool, it should output the number as-is,
no grouping). I came up with:

void
output_binary_string(ostream& os, const string& binary_string)
{
/* If the length of the string (i.e., the number of bits in *
* the binary number), isn't divisable by four, simply output *
* the entire string and return. */
if(binary_string.length() % 4)
{
os << binary_string;

return;
}

string::size_type index = 0;

for(string::size_type i = 0; i < binary_string.length() / 4; ++i)
{
for(int j = 0; j < 4; j++)
{
os << binary_string[index++];
}

os << ' ';
}
}

Now, what if I want to use this function in a cout-statement? Do I have to
create a class or struct then and make my function the overloaded operator<<
for that class/struct?
Right now I do:
cout << "binary_representation: ";
output_binary_string(cout, s);
cout << endl;

I would like to be able to cout << "binary representation: " <<
output_binary_string(cout, s) << endl;

Thanks for any replies


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Jonathan Mcdougall
Guest
PostPosted: Mon Dec 20, 2004 11:34 pm    Post subject: Re: Use stand-alone function in cout-statement Reply with quote


Eric Lilja wrote:
Quote:
Hi, I need a function that expects a const std::string& containing the
visual representation of a number in binary format. It should then output
this number in groups of four bits separated by a space. If the length of
the string is not divisable by four (normally, it should receive 8-bit
numbers (that is, strings of length Cool, it should output the number as-is,
no grouping). I came up with:

void
output_binary_string(ostream& os, const string& binary_string)
{
/* If the length of the string (i.e., the number of bits in *
* the binary number), isn't divisable by four, simply output *
* the entire string and return. */
if(binary_string.length() % 4)
{
os << binary_string;

return;
}

string::size_type index = 0;

for(string::size_type i = 0; i < binary_string.length() / 4; ++i)
{
for(int j = 0; j < 4; j++)
{
os << binary_string[index++];
}

os << ' ';
}
}

Now, what if I want to use this function in a cout-statement? Do I have to
create a class or struct then and make my function the overloaded operator
for that class/struct?
Right now I do:
cout << "binary_representation: ";
output_binary_string(cout, s);
cout << endl;

I would like to be able to cout << "binary representation: "
output_binary_string(cout, s) << endl;

An easy way would be

# include # include <string>

class output_binary_string
{
private:
std::string s_;

public:

output_binary_string(const std::string &s)
: s_(s)
{
}

void print(std::ostream &stream) const
{
stream << s_; // just format it as you wish
}
};

std::ostream &operator<<(std::ostream &stream,
const output_binary_string &obs)
{
obs.print(stream);

return stream;
}


int main()
{
std::string s = "101001010";

std::cout << "Binary: " << output_binary_string(s) << std::endl;
}

You could work out something with manipulators also. Let us know if you
need help.

Jonathan

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Mike Wahler
Guest
PostPosted: Mon Dec 20, 2004 11:40 pm    Post subject: Re: Use stand-alone function in cout-statement Reply with quote



"Eric Lilja" <ericliljaNoSpam (AT) yahoo (DOT) com> wrote

Quote:
Hi, I need a function that expects a const std::string& containing the
visual representation of a number in binary format. It should then output
this number in groups of four bits separated by a space. If the length of
the string is not divisable by four (normally, it should receive 8-bit
numbers (that is, strings of length Cool, it should output the number as-is,
no grouping). I came up with:

void

string

Quote:
output_binary_string(ostream& os, const string& binary_string)

binary_string(const string& binary_string)

Quote:
{
/* If the length of the string (i.e., the number of bits in *
* the binary number), isn't divisable by four, simply output *
* the entire string and return. */

ostringstream os;

Quote:
if(binary_string.length() % 4)
{
os << binary_string;

return;
}

string::size_type index = 0;

for(string::size_type i = 0; i < binary_string.length() / 4; ++i)
{
for(int j = 0; j < 4; j++)
{
os << binary_string[index++];
}

os << ' ';
}

return os.str();

Quote:
}

Now, what if I want to use this function in a cout-statement?


cout << binary_string("10010010") < 'n';

Quote:
Do I have to
create a class or struct then and make my function the overloaded
operator
for that class/struct?
Right now I do:
cout << "binary_representation: ";
output_binary_string(cout, s);
cout << endl;

I would like to be able to cout << "binary representation: "
output_binary_string(cout, s) << endl;

Thanks for any replies

-Mike



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Eric Lilja
Guest
PostPosted: Mon Dec 20, 2004 11:44 pm    Post subject: Re: Use stand-alone function in cout-statement Reply with quote

"Mike Wahler" wrote:
Quote:

"Eric Lilja" <ericliljaNoSpam (AT) yahoo (DOT) com> wrote in message
news:cq7knk$r2n$1 (AT) news (DOT) island.liu.se...
Hi, I need a function that expects a const std::string& containing the
visual representation of a number in binary format. It should then output
this number in groups of four bits separated by a space. If the length of
the string is not divisable by four (normally, it should receive 8-bit
numbers (that is, strings of length Cool, it should output the number
as-is,
no grouping). I came up with:

void

string

output_binary_string(ostream& os, const string& binary_string)

binary_string(const string& binary_string)

{
/* If the length of the string (i.e., the number of bits in *
* the binary number), isn't divisable by four, simply output *
* the entire string and return. */

ostringstream os;

if(binary_string.length() % 4)
{
os << binary_string;

return;
}

string::size_type index = 0;

for(string::size_type i = 0; i < binary_string.length() / 4; ++i)
{
for(int j = 0; j < 4; j++)
{
os << binary_string[index++];
}

os << ' ';
}

return os.str();

}

Now, what if I want to use this function in a cout-statement?


cout << binary_string("10010010") < 'n';

Do I have to
create a class or struct then and make my function the overloaded
operator
for that class/struct?
Right now I do:
cout << "binary_representation: ";
output_binary_string(cout, s);
cout << endl;

I would like to be able to cout << "binary representation: "
output_binary_string(cout, s) << endl;

Thanks for any replies

-Mike



Thanks both Mike and Jonathan for taking the time to help me out! I now
consider this problem solved and I've moved my attention to other issues in
this program. Thanks again.

/ Eric



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