def sympy_to_str(sympy_expr):
'''
sympy_to_str(sympy_expr)
Converts a sympy expression into a string. This could be as easy as
``str(sympy_exp)`` but it is possible that the sympy expression contains
functions like ``Abs`` (for example, if an expression such as
``sqrt(x**2)`` appeared somewhere). We do want to re-translate ``Abs`` into
``abs`` in this case.
Parameters
----------
sympy_expr : sympy.core.expr.Expr
The expression that should be converted to a string.
Returns
str_expr : str
A string representing the sympy expression.
'''
orig_sympy_expr = sympy_expr
# replace the standard functions by our names if necessary
replacements = dict(
(f.sympy_func, sympy.Function(name))
for name, f in DEFAULT_FUNCTIONS.items()
if f.sympy_func is not None and isinstance(
f.sympy_func, sympy.FunctionClass) and str(f.sympy_func) != name)
# replace constants with our names as well
replacements.update(
dict((c.sympy_obj, sympy.Symbol(name))
for name, c in DEFAULT_CONSTANTS.items()
if str(c.sympy_obj) != name))
# Replace the placeholder argument by an empty symbol
replacements[sympy.Symbol('_placeholder_arg')] = sympy.Symbol('')
atoms = (sympy_expr.atoms()
| {f.func
for f in sympy_expr.atoms(sympy.Function)})
for old, new in replacements.items():
if old in atoms:
sympy_expr = sympy_expr.subs(old, new)
expr = PRINTER.doprint(sympy_expr)
return expr
from brian2.core.functions import DEFAULT_FUNCTIONS, DEFAULT_CONSTANTS
from brian2.core.variables import AuxiliaryVariable
from brian2.parsing.bast import (brian_ast, BrianASTRenderer, dtype_hierarchy,
brian_dtype_from_dtype,
brian_dtype_from_value)
from brian2.parsing.rendering import NodeRenderer
from brian2.utils.stringtools import get_identifiers, word_substitute
from brian2.units.fundamentalunits import DIMENSIONLESS
from brian2.core.preferences import prefs
from .statements import Statement
# Default namespace has all the standard functions and constants in it
defaults_ns = dict((k, v.pyfunc) for k, v in DEFAULT_FUNCTIONS.items())
defaults_ns.update(dict((k, v.value) for k, v in DEFAULT_CONSTANTS.items()))
__all__ = ['optimise_statements', 'ArithmeticSimplifier', 'Simplifier']
def evaluate_expr(expr, ns):
'''
Try to evaluate the expression in the given namespace
Returns either (value, True) if successful, or (expr, False) otherwise.
'''
try:
val = eval(expr, ns)
return val, True
except NameError:
return expr, False
