+ // NOTE: The code in simplify_indexed() assumes that canonically
+ // ordered sequences of indices have the two members of dummy index
+ // pairs lying next to each other. The hash values for indices must
+ // be devised accordingly. The easiest (only?) way to guarantee the
+ // desired ordering is to make indices with the same value have equal
+ // hash keys. That is, the hash values must not depend on the index
+ // dimensions or other attributes (variance etc.).
+ // The compare_same_type() methods will take care of the rest.
+ unsigned v = golden_ratio_hash((p_int)tinfo());