Tony Morris

@coltfred Yes, it is two list passes on heap, instead of one on stack.

@dibblego huh, ok. After watching your talk on folds I dug into the source and was immediately baffled. No constructor replacement here?!?

@coltfred You may think of it is constructor replacement, but implemented for some performance -- no infinite lists here.

@dibblego I've always been happy with the "right to left" concept, but constructor replacement is a nice complement to that. Thanks!

@coltfred How do you use "right to left" to explain this? head $ foldr (++) [1..] []

@dibblego #scala is my first FP lang so I'm able to use R to L in my mind, but the concept of replacement is needed for infinite lists.

@coltfred Abandon the explanation. It is a distraction that does not coincide with reality.

@dibblego Noted. I dug into the #scalaz source to find an actual #scala implementation of foldr that made sense based on your talk.