+1 There is a lot of code that is easier to write in "push style" where the code runs blocking and "pushes" results (either to a queue, a callback or a result a

+1 There is a lot of code that is easier to write in "push style" where the code runs blocking and "pushes" results (either to a queue, a callback or a result array that is returned at the end) but it is better for the consumer if it is "pull style" where they can process items as they receive them and can do streaming/incremental parsing. Language supported generation functions/courtesies make it very easy to write in a "push style" while being possible to call in the "pull style".