word_freq.erl in Erlang

A word-frequency table from lexemes, maps:update_with, one sort.

%% Count word frequencies in a passage and chart the leaders.

passage() ->
    "the rain in maine falls mainly on the plain and "
    ++ "the rain stays on the plain".

main(_) ->
    Words = string:lexemes(passage(), " "),

    %% Tally into a map; the default arm seeds new words at zero.
    Counts = lists:foldl(
        fun(W, Acc) -> maps:update_with(W, fun(N) -> N + 1 end, 1, Acc)
        end, #{}, Words),

    %% Rank: count descending, ties broken by the word itself.
    Ranked = lists:sort(
        fun({W1, N1}, {W2, N2}) ->
            if N1 =/= N2 -> N1 > N2;
               true -> W1 =< W2
            end
        end, maps:to_list(Counts)),

    io:format("~p distinct words~n", [length(Ranked)]),
    io:format("word    ct bar~n"),
    [io:format("~-7s ~2B ~s~n", [W, N, lists:duplicate(N, $#)])
     || {W, N} <- Ranked],
    ok.

How it works

1. maps:update_with increments with a seed for new words.
2. The sort fun ranks by count with alphabetical ties.
3. lists:duplicate(N, $#) draws each word's bar.

Keywords and builtins used here

• duplicate
• end
• foldl
• format
• fun
• if
• length
• lexemes
• main
• passage
• sort
• to_list
• update_with

The run, in numbers

Lines

27

Characters to type

731

Tokens

198

Three-star pace

55 tpm

At the three-star pace of 55 tokens a minute, this run takes about 216 seconds.

Type this snippet

Step 1 of 3 in Encore, step 29 of 31 in Language basics.

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