# Bug in expand_delta

+1 vote

There seems to be a bug in expand_delta, or I am making a syntax error of some sort. (I am running the most recent build.)

My code is as follows:

{a,b,c,d}::Indices(vector);
\delta{#}::KroneckerDelta;
ex := \delta^{a}_{b}^{c}_{d};
expand_delta(_);

The error is:

RuntimeError: tree: attempt to navigate up past head node. At:   <string>(6): <module>

## 1 Answer

+1 vote

This only seems to happen when the delta appears at the very top of the expression (so not in a product or sum). Now fixed on github, thanks for reporting.

by (65.1k points)

Thanks, Kasper! I should have realized that was what it was complaining about...