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"""
Module implementing Brian's refractory mechanism.
"""
from brian2.units.allunits import second
from brian2.units.fundamentalunits import DIMENSIONLESS
from .equations import (
BOOLEAN,
DIFFERENTIAL_EQUATION,
PARAMETER,
Equations,
Expression,
SingleEquation,
)
__all__ = ["add_refractoriness"]
def check_identifier_refractory(identifier):
"""
Check that the identifier is not using a name reserved for the refractory
mechanism. The reserved names are `not_refractory`, `refractory`,
`refractory_until`.
Parameters
----------
identifier : str
The identifier to check.
Raises
------
ValueError
If the identifier is a variable name used for the refractory mechanism.
"""
if identifier in ("not_refractory", "refractory", "refractory_until"):
raise SyntaxError(
f"The name '{identifier}' is used in the refractory mechanism "
" and should not be used as a variable "
"name."
)
Equations.register_identifier_check(check_identifier_refractory)
def add_refractoriness(eqs):
"""
Extends a given set of equations with the refractory mechanism. New
parameters are added and differential equations with the "unless refractory"
flag are changed so that their right-hand side is 0 when the neuron is
refractory (by multiplication with the ``not_refractory`` variable).
Parameters
----------
eqs : `Equations`
The equations without refractory mechanism.
Returns
-------
new_eqs : `Equations`
New equations, with added parameters and changed differential
equations having the "unless refractory" flag.
"""
new_equations = []
# replace differential equations having the active flag
for eq in eqs.values():
if eq.type == DIFFERENTIAL_EQUATION and "unless refractory" in eq.flags:
# the only case where we have to change anything
new_code = f"int(not_refractory)*({eq.expr.code})"
new_equations.append(
SingleEquation(
DIFFERENTIAL_EQUATION,
eq.varname,
eq.dim,
expr=Expression(new_code),
flags=eq.flags,
)
)
else:
new_equations.append(eq)
# add new parameters
new_equations.append(
SingleEquation(PARAMETER, "not_refractory", DIMENSIONLESS, var_type=BOOLEAN)
)
new_equations.append(SingleEquation(PARAMETER, "lastspike", second.dim))
return Equations(new_equations)
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