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On success, returns an ambiguity metric. If the parse is unambiguous, the metric is 1. If the parse is ambiguous, the metric is 2 or greater, and is otherwise unspecified. See Better defined ambiguity metric.
If “high rank only” is in effect,
this ambiguity metric may differ from that returned by
marpa_b_ambiguity_metric()
.
In particular, a “high rank only” ordering
may be unambiguous even if its base bocage is ambiguous.
But note also,
because multiple parses choices may have the same rank,
a “high rank only” ordering may be ambiguous.
If the ordering is not already frozen,
it will be frozen on return from
marpa_o_ambiguity_metric()
.
For our purposes,
marpa_o_ambiguity_metric()
is considered an “accessor”,
because it treats its ordering as if it was frozen
before the call to marpa_o_ambiguity_metric()
.
Return value: On success, the ambiguity metric, which is non-negative. On hard failure, -2.
Return value: On success: A number greater than or equal to 1 if the ordering is for a null parse; otherwise, 0. On hard failure, -2.