-module(cases).
-export([insert/2,beach/1]).

insert(X,[]) ->
    [X];
insert(X,Set) ->
    case lists:member(X,Set) of
        true  -> Set;
        false -> [X|Set]
    end.

beach(Temperature) ->
    case Temperature of
        {celsius, N} when N >= 20, N =< 45 ->
            'favorable';
        {kelvin, N} when N >= 293, N =< 318 ->
            'scientifically favorable';
        {fahrenheit, N} when N >= 68, N =< 113 ->
            'favorable in the US';
        _ ->
            'avoid beach'
    end.