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

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 <=
$theta < TWOPI.

=cut

sub mod2pi {return $_[0] - floor ($_[0] / TWOPI) * TWOPI}

=item $theta = mod360( $theta )