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oscherler/occurences.erl

Last active March 6, 2017 16:12
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  1. oscherler revised this gist Mar 6, 2017. 1 changed file with 8 additions and 0 deletions.
    8 changes: 8 additions & 0 deletions occurences.erl
    View file
    Original file line number Diff line number Diff line change
    @@ -1,6 +1,14 @@
    -module( occurences ).
    -export( [ occurences/1 ] ).

    filter( _F, [] ) ->
    [];
    filter( F, [ X | Xs ] ) ->
    case F( X ) of
    true -> [ X | filter( F, Xs ) ];
    _ -> filter( F, Xs )
    end.

    % counts the number of occurrences of each value in a list, and returns a list of tuples,
    % one for each value, containing the value and its occurences.
    %
  2. oscherler created this gist Mar 6, 2017.
    32 changes: 32 additions & 0 deletions occurences.erl
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    Original file line number Diff line number Diff line change
    @@ -0,0 +1,32 @@
    -module( occurences ).
    -export( [ occurences/1 ] ).

    % counts the number of occurrences of each value in a list, and returns a list of tuples,
    % one for each value, containing the value and its occurences.
    %
    % > occurences( [ 1, 2, 3, 2, 1 ] )
    % [{1,2},{2,2},{3,1}]

    occurences( Xs ) ->
    occurences( Xs, [] ).

    occurences( [], R ) ->
    R;
    occurences( [ X | Xs ], R ) ->
    Curr = filter( fun( Y ) ->
    case Y of
    { X, _ } -> true;
    _ -> false
    end
    end, R ),
    New = case Curr of
    [] -> { X, 1 };
    [ { X, N } ] -> { X, N + 1 }
    end,
    NoX = filter( fun( Y ) ->
    case Y of
    { X, _ } -> false;
    _ -> true
    end
    end, R ),
    occurences( Xs, [ New | NoX ] ).