The lists module in Erlang

map, filter, foldl, sort: the daily kit.

%% The lists module: map, filter, foldl, sort -- the daily kit.
main(_) ->
    Durations = [12, 3, 21, 8, 15],

    Billed = lists:map(fun(M) -> M * 4 end, Durations),
    io:format("Pence per call: ~p~n", [Billed]),

    Long = lists:filter(fun(M) -> M > 10 end, Durations),
    io:format("Long calls: ~p~n", [Long]),

    Total = lists:foldl(fun(M, Acc) -> Acc + M end, 0, Durations),
    io:format("Minutes total: ~p~n", [Total]),

    io:format("Sorted: ~p~n", [lists:sort(Durations)]),
    io:format("Longest: ~p~n", [lists:max(Durations)]).

How it works

1. lists:map and filter take funs written inline.
2. foldl threads an accumulator left to right.
3. sort, max, and sum answer the common questions.

Keywords and builtins used here

• end
• filter
• foldl
• format
• fun
• main
• map
• max
• sort

The run, in numbers

Lines

15

Characters to type

510

Tokens

170

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 170 seconds.

Type this snippet

Step 1 of 4 in The lists module, step 11 of 31 in Language basics.

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