-module(lab02).

-import(string,[concat/2]).
-compile(export_all).

%1
mixBeverages(T1, T2) ->
    {concat(concat(element(1, T1), " + "), element(1, T2)), element(2, T1) + element(2, T2)}.

%2
isOlder(D1, D2) ->
    if
        D1 == D2 -> false;
        element(3, D1) < element(3,D2) -> true;
        element(3, D1) > element(3,D2) -> false;
        element(2, D1) < element(2,D2) -> true;
        element(2, D1) > element(2,D2) -> false;
        element(1, D1) < element(1,D2) -> true;
        element(1, D1) > element(1,D2) -> false
    end.


%3
moveDecimal([], _) ->
    [];
moveDecimal([Head|Tail], D3) ->
    [math:pow(10, D3)*Head | moveDecimal(Tail, D3)].

%4
removeNegatives([]) ->
    [];
removeNegatives([Head|Tail]) ->
    if
        Head >= 0 -> [Head|removeNegatives(Tail)];
        true -> removeNegatives(Tail)
    end.

%5
removeNegatives2(L1) ->
    helper(L1).
helper([]) ->
    [];
helper([Head|Tail]) ->
    if
        Head >= 0 -> [Head|helper(Tail)];
        true -> helper(Tail)
    end.

%6
calculatePay(T3) ->
    {element(1, T3), element(2, T3)*element(3, T3)}.

%7
generate(A1, A2, _) when
        A1 > A2 -> [];
generate(A1,A2,A3) when
        (A1 =< A2) -> [A1 | generate(A1+A3, A2, A3)].

%8
getnth([], N) ->
    if
        length([]) == 0 -> {error, no_such_element};
        N < 1 -> {error, no_such_element};
        N > length([]) -> {error, no_such_element}
    end;
getnth([Head|_], 1) ->
    Head;
getnth([_|Tail], N) ->
    getnth(Tail, N-1).

%9
repeat(_, []) ->
    [];
repeat([], _) ->
    [];
repeat([Head1|Tail1], [Head|Tail]) ->
    lists:flatten([lists:duplicate(Head,Head1)|repeat(Tail1,Tail)]).