==============
bitmask module
==============
The central part of this module is the :file:`bitmasks_module.f90` file. It contains
the constants that will be used to define on which kind of integer the bitmasks
will be defined.
In the program, to represent a determinant as a pair of bitstrings,
the determinant should be defined as
.. code-block:: fortran
use bitmasks
integer(bit_kind) :: determinant(N_int,2)
:file:`bitmasks_routines.irp.f` contains helper routines to manipulate bitmask, like
transforming a bit string to a list of integers for example.
`bit_kind_shift`, `bit_kind_size` and `bit_kind` are supposed to be consistent::
2**bit_kind_shift = bit_kind_size
bit_kind = bit_kind_size / 8
For an example of how to use the bitmaks, see the file :file:`example.irp.f`.
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