In order to represent (and modify) a sympy expression within Mathics we've
been using the following:
BasicSympy = sympy.Expr
class SympyExpression(BasicSympy):
is_Function = True
nargs = None
def __new__(cls, expr):
obj = BasicSympy.__new__(
cls, *(expr.head.to_sympy(),) + tuple(leaf.to_sympy()
for leaf in expr.leaves))
obj.expr = expr
return obj
@property
def func(self):
class SympyExpressionFunc(object):
def __new__(cls, *args):
return SympyExpression(self.expr)
return SympyExpressionFunc
def has_any_symbols(self, *syms):
result = any(arg.has_any_symbols(*syms) for arg in self.args)
return result
def _eval_subs(self, old, new):
if self == old:
return new
old, new = from_sympy(old), from_sympy(new)
old_name = old.get_name()
if old_name:
new_expr = self.expr.replace_vars({old_name: new})
return SympyExpression(new_expr)
return self
def _eval_rewrite(self, pattern, rule, **hints):
return self
@property
def is_commutative(self):
if all(getattr(t, 'is_commutative') for t in self.args):
return True
else:
return False
def __str__(self):
return '%s[%s]' % (super(SympyExpression, self).__str__(),
self.expr)
The problem is that sympy.expr._expand_hint has been modified to create a
new sympy.Expr instance (line 2808 of sympy/core/expr.py) rather than using
func. Because SympyExpression overrides __new__ to only accept one
argument, this raises an error.
My original thought was to modify SympyExpression (e.g. a factory that does
some monkey-patching on sympy.Expr), but asmeurer told me that the
implementation in sympy.Expr._expand_hint is wrong.
Should we revert some of the changes in
commit 4b7c2b8199322d8b364b97f6bd27ccaa9dc21dae?
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