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by PeCaN 3791 days ago
foldr usually gets deforested in GHC, so the intermediate list probably doesn't exist.

GHC rewrites most of the common built-in functions to eliminate intermediate trees and lists. You can see a list https://downloads.haskell.org/~ghc/7.0.1/docs/html/users_gui... (section 7.14.4; ctrl-f "good producer").