NAME

Astro::STSDAS::Table::Column - An object representing column information

SYNOPSIS

use Astro::STSDAS::Table::Column;

DESCRIPTION

An Astro::STSDAS::Table::Column object represents a single column in an STSDAS table. It does not store data for the column; it simply manages attributes of the column. The following attributes exist for all columns:

name

the column name

units

the column units

format

the column format

idx

the index of the column in the table (unary based)

Binary table columns have the following additional attributes:

offset

the byte offset from the start of the row (for row ordered tables)

type

the data representation type. See Astro::STSDAS::Table::Constants.

nelem

the number of items in a column element. If the data type is a string, this is the maximum number of characters. if not a string, and if greater than one, it indicates a vector.

fmt

A Perl pack() compatible format used to parse this column. This takes into account the number of elements in a vector.

size

The number of bytes in the data type

ifmt

A Perl pack() compatible format used to parse this column. This does not take into account the number of elements in a vector.

Accessing attributes

Each attribute has an eponymously named method with which the attribute value may be retrieved. The method may also be used to set attributes' values for modifiable attributes. For example:

$oldname = $col->name;
$col->name( $newname );

Modifiable attributes are: name, units, format. If a set of columns is being managed in an Astro::STSDAS::Table::Columns container, it is very important to use that container's rename method to change a column's name, else the container will get very confused.

Other Methods

new

$column = Astro::STSDAS::Table::Column->new(
           $name, $units, $format, $idx, $offset, $type, $nelem );

This is the constructor. It returns an Astro::STSDAS::Table::Column object. Attributes which are inappropriate for the column may be passed as undef. See above for the definition of the attributes. This is generally only called by a Astro::STSDAS::Table::Columns object.

is_string

This returns true if the column is a string column.

is_indef

$bad_value = $col->is_indef( $value );

This determines if the passed value matches the undefined value appropriate to the column.

is_vector

Returns true if the column's elements are vectors.

nelem

This returns the number of items in a column element. This will normally be 1, except for vector columns.

copy

This returns a copy of the column (as an Astro::STSDAS::Table::Column object).

EXPORT

None by default.

LICENSE

This software is released under the GNU General Public License. You may find a copy at

http://www.fsf.org/copyleft/gpl.html

AUTHOR

Diab Jerius (djerius@cpan.org)

SEE ALSO

perl(1).