wrap_dummies

Wraps only the dummy (contracted) indices within the expression using a header symbol.

Similar to wrap_indices, but selectively identifies and wraps only contracted indices (those appearing once upstairs and once downstairs, or twice in a self-dual representation), leaving external (dangling) indices untouched. This is crucial for proper index management in tensor calculations.

Contracted indices are those that:

• Appear in both upper and lower positions (for dualizable reps)
• Appear twice in the same position (for self-dual reps)
• Are summed over (Einstein summation convention)

from symbolica.community.spenso import TensorName, Slot, Representation
import symbolica as sp
from symbolica.community.idenso import simplify_metrics, wrap_dummies

T = TensorName("T")
rep = Representation.euc(3)
# With slots (creates TensorIndices)
mu = rep("mu")
nu = rep("nu")
x = sp.S("x")
tensor_with_args = T(mu, nu, nu, x)  # T(mu, nu; x)
# print(tensor_with_args)
print(wrap_dummies(tensor_with_args.to_expression(), sp.S("wrap")))