empty() ->
[].
+-spec get(t(K, V), K) ->
+ hope_option:t(V).
get(T, K) ->
case lists:keyfind(K, 1, T)
of false -> none
; {K, V} -> {some, V}
end.
+-spec set(t(K, V), K, V) ->
+ t(K, V).
set(T, K, V) ->
lists:keystore(K, 1, T, {K, V}).
+-spec update(t(K, V), K, fun((hope_option:t(V)) -> V)) ->
+ t(K, V).
update(T, K, F) ->
V1Opt = get(T, K),
V2 = F(V1Opt),
% TODO: Eliminate the 2nd lookup.
set(T, K, V2).
+-spec pop(t(K, V), K) ->
+ {hope_option:t(V), t(K, V)}.
pop(T1, K) ->
case lists:keytake(K, 1, T1)
of {value, {K, V}, T2} -> {{some, V}, T2}
; false -> {none , T1}
end.
+-spec iter(t(K, V), fun((K, V) -> ok)) ->
+ ok.
iter(T, F1) ->
F2 = lift_map(F1),
lists:foreach(F2, T).
+-spec map(t(K, V), fun((K, V) -> V)) ->
+ t(K, V).
map(T, F1) ->
F2 = fun ({K, _}=X) -> {K, apply_map(F1, X)} end,
lists:map(F2, T).
+-spec filter(t(K, V), fun((K, V) -> boolean())) ->
+ t(K, V).
filter(T, F1) ->
F2 = lift_map(F1),
lists:filter(F2, T).
+-spec fold(t(K, V), fun((K, V, Acc) -> Acc), Acc) ->
+ Acc.
fold(T, F1, Accumulator) ->
F2 = fun ({K, V}, Acc) -> F1(K, V, Acc) end,
lists:foldl(F2, Accumulator, T).
+-spec to_kv_list(t(K, V)) ->
+ [{K, V}].
to_kv_list(T) ->
T.
+-spec of_kv_list([{K, V}]) ->
+ t(K, V).
of_kv_list(List) ->
% TODO: Decide if validation is to be done here. Do so if yes.
List.