03 - formatted I/O

#include <iostream>

int main()
{
	std::cout << std::boolalpha   << true << " " << false << "\n";
	std::cout << std::noboolalpha << true << " " << false << "\n"; // default
}

#include <iostream>

int main()
{
	std::cout << std::showpos   << -1 << " " << 1 << "\n";
	std::cout << std::noshowpos << -1 << " " << 1 << "\n"; // default
}

#include <iostream>

int main()
{
	std::cout << std::showbase; // enable printing base prefix (0 for octal, 0x for hex)
	std::cout << "in octal       (base  8): " << std::oct << 42 << "\n";
	std::cout << "in decimal     (base 10): " << std::dec << 42 << "\n";
	std::cout << "in hexadecimal (base 16): " << std::hex << 42 << "\n";

	std::cout << "\n";

	std::cout << std::noshowbase; // disable printing base prefix (default)
	std::cout << "in octal       (base  8): " << std::oct << 42 << "\n";
	std::cout << "in decimal     (base 10): " << std::dec << 42 << "\n";
	std::cout << "in hexadecimal (base 16): " << std::hex << 42 << "\n";
}

#include <iostream>
#include <sstream>

int main()
{
	int x = 0;
	int y = 0;
	std::istringstream iss("10 010");
	// comment/uncomment line below for different parsing behavior
	// iss.setf(std::ios_base::fmtflags(0), std::ios_base::basefield);
	iss >> x >> y;
	//   commented: 10 10 (default state has dec bit on),
	// uncommented: 10 8  (no base bits cause parsing to depend on prefix)
	std::cout << x << " " << y << "\n";
}

#include <iostream>

int main()
{
	std::cout << std::hex << std::showbase;
	std::cout << std::uppercase   << 0xdeadbeef << " " << 123456789.0 << "\n";
	std::cout << std::nouppercase << 0xdeadbeef << " " << 123456789.0 << "\n"; // default
}

#include <iostream>

int main()
{
	std::cout << std::showpoint   << 1.0 << " " << 12.34 << "\n";
	std::cout << std::noshowpoint << 1.0 << " " << 12.34 << "\n"; // default
}

#include <iostream>

int main()
{
	std::cout << "0.001 in fixed:      " << std::fixed        << 0.001 << "\n"; // ignores showpoint
	std::cout << "0.001 in scientific: " << std::scientific   << 0.001 << "\n";
	std::cout << "0.001 in hexfloat:   " << std::hexfloat     << 0.001 << "\n"; // ignores precision
	std::cout << "0.001 in default:    " << std::defaultfloat << 0.001 << "\n"; // this is the default

	std::cout << "\n";

	std::cout << " 1000 in fixed:      " << std::fixed        << 1000.0 << "\n";
	std::cout << " 1000 in scientific: " << std::scientific   << 1000.0 << "\n";
	std::cout << " 1000 in hexfloat:   " << std::hexfloat     << 1000.0 << "\n";
	std::cout << " 1000 in default:    " << std::defaultfloat << 1000.0 << "\n";
}

#include <iostream>
#include <sstream>

int main()
{
	const auto text = "a b c d";
	std::istringstream iss;
	char c = '\0';

	iss.str(text);
	iss >> std::skipws; // default behavior (this statement has no effect)
	while (iss >> c) // will stop on reaching end of internal string buffer and set EOF
	{
		std::cout << "[" << c << "], ";
	}

	std::cout << "\n";
	iss.clear(); // clear EOF

	iss.str(text);
	iss >> std::noskipws;
	while (iss >> c)
	{
		std::cout << "[" << c << "], ";
	}
}

#include <iostream>
#include <iomanip>

int main()
{
	// adjust left and fill with *
	std::cout << std::left << std::setfill('*');
	for (long i = 1; i < 1000000000; i *= 10)
		std::cout << std::setw(8) << i << "\n";

	std::cout << "\n";

	// adjust right and fill with .
	std::cout << std::right << std::setfill('.');
	for (long i = 1; i < 1000000000; i *= 10)
		std::cout << std::setw(8) << i << "\n";

	std::cout << "\n";

	// use hex base and print prefix, fill with _
	// adjust numbers to the right but other characters to the left
	std::cout << std::hex << std::showbase;
	std::cout << std::internal << std::setfill('_');
	for (long i = 1; i < 1000000000; i *= 10)
		std::cout << std::setw(8) << i << "\n";
}

#include <iostream>
#include <iomanip>
#include <cmath>
#include <limits>

int main()
{
	const long double pi = std::acos(-1.0l); // (arc cosine)
	constexpr auto maxp = std::numeric_limits<long double>::digits10 + 1;
	std::cout << "default precision (6): " << pi << "\n"
	          << "std::setprecision(10): " << std::setprecision(10) << pi << "\n"
	          << "max precision        : " << std::setprecision(maxp) << pi << "\n\n";


	// This value will likely not be ideal half due to
	// limited accuracy of floating-point computations.
	const auto almost_half = std::acos(0.0) / pi;

	// Setting precision larger than supported by the underlying
	// floating point type will cause weird output.
	// This is because streams always try to print the value (in decimal)
	// that is closest to the actually stored value (in floating-point).
	// Thus, 0.5 is choosen over 0.4999999999999999 (the first one is more accurate).
	// Once the precision allows to represent this tiny error, output changes.
	for (int i = 6; i < maxp + 3; ++i)
		std::cout << std::setprecision(i) << almost_half << "\n";
}