Do calls f from parallelism goroutines n times, providing each invocation a unique i in [0, n).

DoContext calls f from parallelism goroutines n times, providing each invocation a unique i in [0, n).

Map uses parallelism goroutines to call f once for each element of in.

MapContext uses parallelism goroutines to call f once for each element of in.

MapIterator uses parallelism goroutines to call f once for each element yielded by iter.

MapStream uses parallelism goroutines to call f once for each element yielded by s.