Empty clauses, such as those produced by nil, are dropped first; a single surviving clause is returned
as-is, while several are wrapped in groups and joined with union. When none survives, the result
is the empty fragment via nil, which callers must guard against where a pattern is required.
Generates a SPARQL
UNIONpattern.Empty clauses, such as those produced by nil, are dropped first; a single surviving clause is returned as-is, while several are wrapped in groups and joined with
union. When none survives, the result is the empty fragment via nil, which callers must guard against where a pattern is required.