cln_mirror/examples/pi.cc

// Compute decimal Archimedes' constant Pi to arbitrary accuracy.

#include <cln/output.h>
#include <cln/real.h>
#include <cln/real_io.h>
#include <cln/version.h>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <sstream>

using namespace std;
using namespace cln;

static void
usage (ostream &os)
{
	os << "Usage: pi [digits]\n";
	os << "Compute decimal Archimedes' constant Pi to arbitrary accuracy.\n\n";
	os << "      --help                 display this help and exit\n";
	os << "      --version              output version information and exit\n";
	os << "      --bibliography         output recommended readings and exit\n";
}

int
main (int argc, char * argv[])
{
	long digits = 100;
	if (argc > 1) {
		if (argc == 2 && !strcmp(argv[1],"--help")) {
			usage(cout);
			return 0;
		}
		if (argc == 2 && !strcmp(argv[1],"--version")) {
			cout << "pi (CLN "
			     << version_major << "." << version_minor << "." << version_patchlevel
			     << ")" << endl;
			cout << "Written by Bruno Haible and Richard B. Kreckel." << endl;
			cout << endl;
			cout << "Copyright (C) 1988-2008 Bruno Haible, 2000-2009 Richard B. Kreckel." << endl;
			cout << "This is free software; see the source for copying conditions.  There is NO" << endl;
			cout << "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE." << endl;
			cout << endl;
			return 0;
		}
		if (argc == 2 && !strcmp(argv[1],"--bibliography")) {
			cout << "Recommended readings:\n";
			cout << "\"Pi\", by Joerg Arndt and Christoph Haenel (1999)\n";
			cout << "\"Pi: A Source Book\" by Lennart Berggren, Jonathan Borwein, Peter Borwein (1997)" << endl;
			return 0;
		}
		if (argc == 2 && isdigit(argv[1][0])) {
			digits = atol(argv[1]);
		} else {
			usage(cerr);
			return 1;
		}
	}

	if (digits) {
		cl_F p = pi(float_format(digits));
		// make CLN believe this number has default_float_format to suppress
		// exponent marker which would be quite boring for 3.1416...
		cl_print_flags cpf;
		cpf.default_float_format = float_format(p);
		// We cannot print directly because people get dazed and confused
		// when they see gratuitous digits (Debian Bug #286266.) And we
		// must not "fix" the output routine because print-read consistency
		// is at stake. As a workaround, print into a buffer so we can chop
		// off characters from its end.
		stringstream buf;
		print_real(buf, cpf, p);
		istreambuf_iterator<char> i = buf.rdbuf();
		while (--digits+2>0)
			cout << *(i++);
	}
	cout << endl;

	return 0;
}