NAME

Demeter::Constants - A library of constants

VERSION

This documentation refers to Demeter version 0.9.26.

SYNOPSIS

This provides a library of constants so as to avoid redefining then over and over.

  use Demeter::Constants qw(:all);

  use Demeter::Constants qw($NUMBER);

DESCRIPTION

This collects all the commonly defined constants into one place. Please note that this exports variables into your module's namespace. This is a against good practice, but is a huge convenience, they are all upper case, and I am telling you about it!

The :all tag can be used to import the entire library.

Numbers

The following constants are numbers. They can be imported as a set using the :numbers export tag.

$PI

This is 4*atan2(1,1).

$ETOK

The conversion constant between energy and wavenumber.

  k = sqrt( ETOK * (E-E0) )

$ETOK is about equal to 1 / 3.81. 10 inverse Angstroms is about 381 volts above the edge.

$HBARC

This is hbar*c in eV*Angstrom units.

$HC

This is h*c in eV*Angstrom units.

  $HC = $HBARC * 2 * $PI;

$HBARC

This is hbar in eV*seconds units.

$R2D

The conversion constant between degrees and radians, 180/PI.

$EPSILONn

1e-n, for instance $EPSILON2 = 1e-2 and $EPSILON2 = 1e-7. These are defined for 2 through 7.

Strings

The following constants are strings. They can be imported as a set using the :strings export tag.

$NULLFILE: This is @&^^null^^&@, a nonesense string to indicate an undefined filename.
$ENDOFLINE: The platform specific end of line character.
$CTOKEN: The token, +, denoting the central atom in a short representation of the path geometry.

Regular expressions

The following constants are regular expressions. They can be imported as a set using the :regexps export tag.

$NUMBER: This is $RE{num}{real} from Regexp::Common, i.e. a match for floats.
$INTEGER: This is $RE{num}{int} from Regexp::Common, i.e. a match for integers.
$SEPARATOR: This is [ \t]*[ \t=,][ \t]*, the regular expression defining the separation between keyword and value in an input file for Feff, Atoms, etc.
$ELEMENT: A regular expression matching a valid element symbol.
$FEFFNOTOK: A regular expression used to scrub strings which, when used as site tags, will cause trouble with Feff. This currently matches a character that is not alphanumeric, a dot, a dash, or an underscore: [^-a-zA-Z0-9_.]

BUGS AND LIMITATIONS

Please report problems to the Ifeffit Mailing List (http://cars9.uchicago.edu/mailman/listinfo/ifeffit/)

Patches are welcome.

AUTHOR

Bruce Ravel, http://bruceravel.github.io/home

http://bruceravel.github.io/demeter/

LICENCE AND COPYRIGHT

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlgpl.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.