On iteration and enumeration

[josevalim]

@Qqwy

:maps.map/2 is the Functor mapping function for maps. The reasoning is as follows: Since maps cannot contain duplicate keys, the structure would be changed if a mapping operation would also allow altering the keys. Thus, the return value of the function passed to map/2 is the value that is used for the current key at all times.

And maps:map2 converts to a list and then converts it back to a map, which goes back to my earlier point of it all being done on lists anyway: otp/lib/stdlib/src/maps.erl at master · erlang/otp · GitHub

BIFs do not accept anonymous function as argument and I don’t believe there is a plan to lift this restriction. So it is probably staying like this for now.

@Qqwy

Related to this is the Extractable library I wrote a couple of months back, which allows you to enumerate collections in a one-item-per-time fashion

Does it work with resources? Because it was one of the first approaches that we tried but very error prone when it comes to dangling resources.