[davedx]

That kind of thing really depends on the language. Some of the stronger functional languages like Haskell have lazy evaluation, so that operation won't be as bad as it looks. But then you really need to fully understand the tradeoffs of lazy evaluation too.

[kreyenborgi]

or list fusion, but yes Haskell will optimise map x (map y lst) to map (x . y) lst

https://stackoverflow.com/questions/38905369/what-is-fusion-...