Erlang list comprehension with two lists in sequence?

Question

Is it possible to use list comprehension on two lists, item by item, in sequence? Given A = [1,2,3], B = [4,5,6], get some C = [f(1, 4), f(2, 5), f(3, 6)]. In other words, a more direct/efficient way to do [f(U, V) || {U, V} = lists:zip(A, B)].

Similar question goes to binaries, if given A = <<1,2,3>> and B = <<4,5,6>>. This would be very useful if you have to xor two binaries, for example.

score 8 · Accepted Answer · edited Oct 26 '16 at 08:30

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It's not currently possible. It has already been proposed in EEP12 and EEP19.

Your best choice is to implement your own recursive function for that.

edited Oct 26 '16 at 08:30

Community

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answered Dec 17 '09 at 18:05

Zed

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score 3 · Answer 2 · answered Dec 18 '09 at 18:30

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There is already a higher-order-function in the lists module for this and it is called lists:zipwith/3. Your example scenario would be implemented this way:

lists:zipwith(fun f/2, A, B).

answered Dec 18 '09 at 18:30

Christian

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Yes, there are functions for zipping two or three lists. But there is no general solution for N lists, as a list comprehension would be. – Zed Dec 19 '09 at 18:59

Erlang list comprehension with two lists in sequence?

2 Answers2