Some very common (and useful) operations, including the classic map, filter, and flat_map, traverse their whole argument and return another collection. When several such operations are composed, intermediate collections will be created and become useless immediately after. Languages like Haskell sometimes perform optimizations that merge together the operations so as to minimize the number of intermediate collections : map f . map g == map (f . g) Sadly, the OCaml compiler performs very few o...
