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lib/Astro/Coord/ECI/Utils.pm  view on Meta::CPAN

    my $Century = $NextCentury - 100;

    # The above code is lifted verbatim from Time::Local 1.25.

    use constant NOT_GREG	=>
	'%d not interpreted as Gregorian year by Time::Local::timegm';

    # Adujst the year so that the Time::y2038 implementation of
    # time_gm() and time_local() mirrors the Time::Local timegm() and
    # timelocal() behavior. Kinda sorta.
    sub _year_adjust_y2038 {
	my ( $year ) = @_;

	$year < 0
	    and return $year;

	$year >= 1000
	    and return $year - 1900;

	# The following line of code is lifted verbatim from Time::Local
	# 1.25.
	$year += ( $year > $Breakpoint ) ? $Century : $NextCentury;

	return $year;
    }
}

# Adjust a Gregorian year so that Time::Local timegm() and timelocal()
# return epochs in that year.
sub _year_adjust_greg {
    my ( $year ) = @_;
    return $year >= 1000 ? $year : $year - 1900;
}

our @CARP_NOT = qw{
    Astro::Coord::ECI
    Astro::Coord::ECI::Mixin
    Astro::Coord::ECI::Moon
    Astro::Coord::ECI::Star
    Astro::Coord::ECI::Sun
    Astro::Coord::ECI::TLE
    Astro::Coord::ECI::TLE::Set
    Astro::Coord::ECI::Utils
};

our @EXPORT;
my @all_external = ( qw{
	AU $DATETIMEFORMAT $JD_GREGORIAN JD_OF_EPOCH LIGHTYEAR PARSEC
	PERL2000 PI PIOVER2
	SECSPERDAY SECS_PER_SIDERIAL_DAY SECS_PER_TROPICAL_YEAR
	SPEED_OF_LIGHT TWOPI
	ARRAY_REF CODE_REF HASH_REF SCALAR_REF
	acos add_magnitudes asin
	atmospheric_extinction date2epoch date2jd
	decode_space_track_json_time deg2rad distsq dynamical_delta
	embodies epoch2datetime find_first_true
	fold_case __format_epoch_time_usec
	format_space_track_json_time gm_strftime intensity_to_magnitude
	jcent2000 jd2date jd2datetime jday2000 julianday
	keplers_equation load_module local_strftime
	looks_like_number max min mod2pi mod360
	omega position_angle
	rad2deg rad2dms rad2hms tan theta0 thetag vector_cross_product
	vector_dot_product vector_magnitude vector_unitize __classisa
	__default_station __instance __subroutine_deprecation
	__sprintf
	},
	qw{ time_gm time_local }, @greg_time_routines );
our @EXPORT_OK = (
    qw{ @CARP_NOT },	# Package-private, undocumented
    @all_external,
);

my %deprecated_export = map { $_ => 1 } qw{
};

our %EXPORT_TAGS = (
    all => \@all_external,
    greg_time	=> \@greg_time_routines,
    mainstream => [ grep { ! $deprecated_export{$_} } @all_external ],
    params => [ qw{ __classisa __instance } ],
    ref	=> [ grep { m/ [[:upper:]]+ _REF \z /smx } @all_external ],
    time => [ qw{ gm_strftime local_strftime time_gm time_local },
	@greg_time_routines ],
    vector => [ grep { m/ \A vector_ /smx } @all_external ],
);

use constant AU => 149597870;		# 1 astronomical unit, per
					# Meeus, Appendix I pg 407.
use constant LIGHTYEAR => 9.4607e12;	# 1 light-year, per Meeus,
					# Appendix I pg 407.
use constant PARSEC => 30.8568e12;	# 1 parsec, per Meeus,
					# Appendix I pg 407.
use constant PERL2000 => greg_time_gm( 0, 0, 12, 1, 0, 2000 );
use constant PI => atan2 (0, -1);
use constant PIOVER2 => PI / 2;
use constant SECSPERDAY => 86400;
use constant SECS_PER_SIDERIAL_DAY => 86164.0905;	# Appendix I, page 408.
# Meeus Appendix I
use constant SECS_PER_TROPICAL_YEAR	=> 365.242190 * SECSPERDAY;
use constant SPEED_OF_LIGHT => 299792.458;	# KM/sec, per NIST.
### use constant SOLAR_RADIUS => 1392000 / 2;	# Meeus, Appendix I, page 407.
use constant TWOPI => PI * 2;

use constant ARRAY_REF	=> ref [];
use constant CODE_REF	=> ref sub {};
use constant HASH_REF	=> ref {};
use constant SCALAR_REF	=> ref \0;

=item $angle = acos ($value)

This subroutine calculates the arc in radians whose cosine is the given
value.

=cut

sub acos {
    abs ($_[0]) > 1 and confess <<eod;
Programming error - Trying to take the arc cosine of a number greater
        than 1.
eod

lib/Astro/Coord/ECI/Utils.pm  view on Meta::CPAN

    my $prev;
    # Meeus' equation 30.7, page 199.
    {
	$prev = $curr;
	my $delta = ( $mean_anomaly + $eccentricity * sin( $curr
	    ) - $curr ) / ( 1 - $eccentricity * cos $curr );
	# Steele's correction, page 205
	$curr = $curr + max( -.5, min( .5, $delta ) );
	$precision < abs( $curr - $prev )
	    and redo;
    }
    return $curr;
}

=item $rslt = load_module ($module_name)

This convenience method loads the named module (using 'require'),
throwing an exception if the load fails. If the load succeeds, it
returns the result of the 'require' built-in, which is required to be
true for a successful load.  Results are cached, and subsequent attempts
to load the same module simply give the cached results.

=cut

{	# Local symbol block. Oh, for 5.10 and state variables.
    my %error;
    my %rslt;
    sub load_module {
	my  ($module) = @_;
	exists $error{$module} and croak $error{$module};
	exists $rslt{$module} and return $rslt{$module};
	# I considered Module::Load here, but it appears not to support
	# .pmc files. No, it's not an issue at the moment, but it may be
	# if Perl 6 becomes a reality.
	$rslt{$module} = eval "require $module"
	    or croak( $error{$module} = $@ );
	return $rslt{$module};
    }
}	# End local symbol block.

=item print local_strftime( $format, $epoch, $places )

This subroutine takes as input a strftime-compatible format and an
epoch, and returns the local time, formatted per the format.

Optional argument C<$places> is the default number of decimal places for
seconds. If defined, it must be either C<''> or an unsigned integer.

You can also specify an optional C<'.d'> (where the 'd' is one or more
decimal digits) before any format specification that generates seconds.
Examples include C<'%.3S'> or C<'%.6T'>. Such a specification overrides
the C<$places> argument, if any.

=cut

sub local_strftime {
    my ( $format, $epoch ) = _pre_strftime( @_ );
    return POSIX::strftime( $format, localtime $epoch );
}

=item $boolean = looks_like_number ($string);

This subroutine returns true if the input looks like a number. It uses
Scalar::Util::looks_like_number if that is available, otherwise it uses
its own code, which is lifted verbatim from Scalar::Util 1.19, which in
turn leans heavily on perlfaq4.

=cut

unless (eval {require Scalar::Util; Scalar::Util->import
	('looks_like_number'); 1}) {
    no warnings qw{once};
    *looks_like_number = sub {
	local $_ = shift;

	# checks from perlfaq4
	return 0 if !defined($_) || ref($_);
	return 1 if (/^[+-]?[0-9]+$/); # is a +/- integer
	return 1 if (/^([+-]?)(?=[0-9]|\.[0-9])[0-9]*(\.[0-9]*)?([Ee]([+-]?[0-9]+))?$/); # a C float
	return 1 if ($] >= 5.008 and /^(Inf(inity)?|NaN)$/i)
	    or ($] >= 5.006001 and /^Inf$/i);

	return 0;
    };
}

=item $maximum = max (...);

This subroutine returns the maximum of its arguments.  If List::Util can
be loaded and 'max' imported, that's what you get. Otherwise you get a
pure Perl implementation.

=cut

unless (eval {require List::Util; List::Util->import ('max'); 1}) {
    no warnings qw{once};
    *max = sub {
	my $rslt;
	foreach (@_) {
	    defined $_ or next;
	    if (!defined $rslt || $_ > $rslt) {
		$rslt = $_;
	    }
	}
	$rslt;
    };
}

=item $minimum = min (...);

This subroutine returns the minimum of its arguments.  If List::Util can
be loaded and 'min' imported, that's what you get. Otherwise you get a
pure Perl implementation.

=cut

unless (eval {require List::Util; List::Util->import ('min'); 1}) {
    no warnings qw{once};
    *min = sub {
	my $rslt;
	foreach (@_) {
	    defined $_ or next;
	    if (!defined $rslt || $_ < $rslt) {
		$rslt = $_;
	    }
	}
	$rslt;
    };
}

=item $theta = mod2pi ($theta)

This subroutine reduces the given angle in radians to the range 0 <=