I would like to create a subclass of SymbolicRing to allow variables that are indexed without shoving this information into the variables names, e.g. I would prefer not to use variables with names like x_1_1_1 and I would like to be able to access the indices without parsing the name.
This seems to be supported using _repr_element_, e.g. CallableSymbolicExpressionRing overrides this method. I would like to implement this with minimal change to SymbolicRing or Expression as the only functionality I want to change is how the expressions are displayed and the addition of a variable keeping track of the indices.
When I try to do this, the resulting expressions revert back after applying any operations... Any advice would be appreciated!
from sage.all import *
from sage.symbolic.ring import SymbolicRing
from sage.symbolic.expression import Expression
class IndexedExpression(Expression):
def __init__(self, var_name, indices):
formatted_var_name = var_name + "_" + "_".join(str(i) for i in indices)
super().__init__(SR, SR.var(formatted_var_name))
self._name = var_name
self._indices = indices
self._parent = SR
def _repr_(self):
return self._parent._repr_element_(self)
class IndexedSymbolicExpressionRing(SymbolicRing):
def var(self, var_name, indices):
expr = IndexedExpression(var_name, indices)
expr._parent = self
return expr
def _repr_(self):
return "Indexed Symbolic Expression Ring"
def _repr_element_(self, x):
return f"{x._name}{x._indices}"
ISR = IndexedSymbolicExpressionRing()
y = ISR.var("y", [1, 1])
print(y) # y[1, 1]
print(y + y) # 2*y_1_1 instead of 2*y[1, 1]
