i followed (and enjoyed) most of that, but i don't get (perhaps because i've not used haskell in a long time) how the consumer is automatically(?) chosen.

from what i understand of section 3.2 the consumer is critical in selecting the correct stream type from the bundle. who decides that? does the user have to select the appropriate function? or does it some how fall out naturally from the use case? or does the compiler select it?