- public xfunc/xfn, xpred
- where_not?
- invalidate/invalidate_all() to (make|silent)_lookuper?
- decorators with optional arguments?
- pre_walk, post_walk
- tree-seq
- (log|print)_errors to optionally hide causing call
- log_* and print_* to optionally hide args
- padding to chunks
- partial.func interface or (func, arg1, arg2) extended fns
- reject*(), disjoint*() collections
- zip_with = map(f, zip(seqs))
- starfilter()
- one argument select*()? other name?
- reversed() to work with iterators
- vector chained boolean test (like perl 6 [<])
- cython implementation? separate - cyfuncy? fallback transparently?
- funcyx?