#!/usr/bin/env perl
use utf8;
###############################################################################
# This program demonstrates a significant digits rounding function.
# 
# Copyright © 2017 Richard Lesh.  All rights reserved.
###############################################################################

use Math::Trig qw(pi);
use POSIX qw(floor log10);
use Utils;
use strict;
use warnings;

sub round_sig_dig {
    my ($value, $sigdigits) = @_;
    if ($value == 0.0) {
        return 0.0;
    }
    my $p = ((10.0) ** ($sigdigits - int(floor(log10(abs($value)))) - 1));
    return floor($value * $p + 0.5) / $p;
}

MAIN:
{
    binmode(STDOUT, ":utf8");
    binmode(STDERR, ":utf8");
    binmode(STDIN, ":utf8");
# Test with π
    for (my $sd = 1; $sd <= 16; ++$sd) {
        print Utils::messageFormat("π to \{0:d\} significant digits: \{1:.16f\}", $sd, round_sig_dig(pi(), $sd)), "\n";
    }

# Test with ℯ
    for (my $sd = 1; $sd <= 16; ++$sd) {
        print Utils::messageFormat("ℯ to \{0:d\} significant digits: \{1:.16f\}", $sd, round_sig_dig(exp(1.), $sd)), "\n";
    }

# Test with 1/π
    for (my $sd = 1; $sd <= 16; ++$sd) {
        print Utils::messageFormat("1/π to \{0:d\} significant digits: \{1:.16e\}", $sd, round_sig_dig(1.0 / pi(), $sd)), "\n";
    }

# Test with 1e-6/e
    for (my $sd = 1; $sd <= 16; ++$sd) {
        print Utils::messageFormat("1e-6/e to \{0:d\} significant digits: \{1:.16e\}", $sd, round_sig_dig(1e-6 / exp(1.), $sd)), "\n";
    }
}