Catch users who try to index UFL expressions with negative indices (F…

…EniCS#66) Co-authored-by: Patrick Farrell <[email protected]>
firedrakeproject · Aug 13, 2021 · a41f5b6 · a41f5b6
1 parent 94badf8
commit a41f5b6
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/ufl/indexed.py b/ufl/indexed.py
@@ -62,7 +62,7 @@ def __init__(self, expression, multiindex):
             error("Invalid number of indices (%d) for tensor "
                   "expression of rank %d:\n\t%s\n"
                   % (len(multiindex), len(expression.ufl_shape), ufl_err_str(expression)))
-        if any(int(di) >= int(si)
+        if any(int(di) >= int(si) or int(di) < 0
                for si, di in zip(shape, multiindex)
                if isinstance(di, FixedIndex)):
             error("Fixed index out of range!")