def bddvar(name, index=None):
r"""Return a unique BDD variable.
A Boolean *variable* is an abstract numerical quantity that may assume any
value in the set :math:`B = \{0, 1\}`.
The ``bddvar`` function returns a unique Boolean variable instance
represented by a binary decision diagram.
Variable instances may be used to symbolically construct larger BDDs.
A variable is defined by one or more *names*,
and zero or more *indices*.
Multiple names establish hierarchical namespaces,
and multiple indices group several related variables.
If the ``name`` parameter is a single ``str``,
it will be converted to ``(name, )``.
The ``index`` parameter is optional;
when empty, it will be converted to an empty tuple ``()``.
If the ``index`` parameter is a single ``int``,
it will be converted to ``(index, )``.
Given identical names and indices, the ``bddvar`` function will always
return the same variable:
>>> bddvar('a', 0) is bddvar('a', 0)
True
To create several single-letter variables:
>>> a, b, c, d = map(bddvar, 'abcd')
To create variables with multiple names (inner-most first):
>>> fifo_push = bddvar(('push', 'fifo'))
>>> fifo_pop = bddvar(('pop', 'fifo'))
.. seealso::
For creating arrays of variables with incremental indices,
use the :func:`pyeda.boolalg.bfarray.bddvars` function.
"""
bvar = boolfunc.var(name, index)
try:
var = _VARS[bvar.uniqid]
except KeyError:
var = _VARS[bvar.uniqid] = BDDVariable(bvar)
_BDDS[var.node] = var
return var
def ttvar(name, index=None):
"""Return a TruthTable variable.
Parameters
----------
name : str
The variable's identifier string.
index : int or tuple[int], optional
One or more integer suffixes for variables that are part of a
multi-dimensional bit-vector, eg x[1], x[1][2][3]
"""
bvar = boolfunc.var(name, index)
try:
var = _TTVARIABLES[bvar.uniqid]
except KeyError:
var = _TTVARIABLES[bvar.uniqid] = TTVariable(bvar)
return var
def bddvar(name, index=None):
r"""Return a unique BDD variable.
A Boolean *variable* is an abstract numerical quantity that may assume any
value in the set :math:`B = \{0, 1\}`.
The ``bddvar`` function returns a unique Boolean variable instance
represented by a binary decision diagram.
Variable instances may be used to symbolically construct larger BDDs.
A variable is defined by one or more *names*,
and zero or more *indices*.
Multiple names establish hierarchical namespaces,
and multiple indices group several related variables.
If the ``name`` parameter is a single ``str``,
it will be converted to ``(name, )``.
The ``index`` parameter is optional;
when empty, it will be converted to an empty tuple ``()``.
If the ``index`` parameter is a single ``int``,
it will be converted to ``(index, )``.
Given identical names and indices, the ``bddvar`` function will always
return the same variable:
>>> bddvar('a', 0) is bddvar('a', 0)
True
To create several single-letter variables:
>>> a, b, c, d = map(bddvar, 'abcd')
To create variables with multiple names (inner-most first):
>>> fifo_push = bddvar(('push', 'fifo'))
>>> fifo_pop = bddvar(('pop', 'fifo'))
.. seealso::
For creating arrays of variables with incremental indices,
use the :func:`pyeda.boolalg.bfarray.bddvars` function.
"""
bvar = boolfunc.var(name, index)
try:
var = _VARS[bvar.uniqid]
except KeyError:
var = _VARS[bvar.uniqid] = BDDVariable(bvar)
_BDDS[var.node] = var
return var
