Subscript a crystal Object

DESCRIPTION:
Allows the user to extract or replace parts of a crystal object by using crystal names or subscripts.

USAGE:
x[i]
x[i, left=T, right=T] <- value
x[[i]]

REQUIRED ARGUMENTS:
x:
an object of class wp.crystal, wp.inf.crystal, or cp.crystal.
i:
a vector of crystal names, positive integers or logical flags. For [[, i must be an integer or a crystal name.

OPTIONAL ARGUMENTS:
value:
replacement value for the relevant piece of the crystal object.
left:
for assignment operator only, a logical flag indicating if the left boundary coefficients are to be set to zero.
right:
for assignment operator only, a logical flag indicating if the right boundary coefficients are to be set to zero.

VALUE:
x[i] returns an object of class "wp.molecule" or "cp.molecule", inheriting from class "molecule"; x[[i]] returns an object of class "wp.atom" or "cp.atom".

DETAILS:
Special assignment operator is needed for wp.inf.crystal objects only. The default assignment operator is used for wp.crystal and cp.crystal objects.

SEE ALSO:
wp.crystal , wp.inf.crystal , cp.crystal, wp.crystal.object , wp.inf.crystal.object , cp.crystal.object, molecule.object , wp.atom.object , cp.atom.object .