The reduce arity of IReduce in PersistentVector is implemented as: "throw new UnsupportedOperationException()".
After the CLJ-1572 patch is applied the following code will throw:
(reduce + [1 2])
Approach taken: Implement reduce(f) in PersistentVector.
Alternative: An alternate would be to change PersistentVector from IReduce to IReduceInit and remove the reduce without init function. In this case, reducing a vector would fall back to seqs.
Screened by: Stu