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gb_trees_ext.erl
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/
gb_trees_ext.erl
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%% Copyright
-module(gb_trees_ext).
-author("eshubin").
%% API
-export([lower_bound/2]).
lower_bound(Key, {_, T}) ->
lower_bound_1(Key, T, []).
lower_bound_1(Key, {Key1, _, Smaller, _} = T, As) when Key < Key1 ->
lower_bound_1(Key, Smaller, [T | As]);
lower_bound_1(Key, {Key1, _, _, Bigger}, As) when Key > Key1 ->
lower_bound_1(Key, Bigger, As);
lower_bound_1(Key, {Key1, _, _, _} = T, As) when Key == Key1 ->
[T | As];
lower_bound_1(_, nil, As) ->
As.
-include_lib("eunit/include/eunit.hrl").
lower_bound_test_() ->
{
setup,
fun() ->
gb_trees:from_orddict([{X, X} || X <- lists:seq(0, 20, 2)])
end,
fun(Tree) ->
[
?_assertEqual([], lower_bound(3, gb_trees:empty())),
?_assertMatch({4,4,_}, gb_trees:next(lower_bound(3, Tree))),
?_assertMatch({4,4,_}, gb_trees:next(lower_bound(4, Tree))),
?_assertMatch(none, gb_trees:next(lower_bound(40, Tree))),
?_assertMatch({6,6,_}, gb_trees:next(lower_bound(5, Tree))),
?_test(
begin
{K1, V1, I2} = gb_trees:next(lower_bound(17, Tree)),
?assertEqual({18,18}, {K1, V1}),
{K2, V2, I3} = gb_trees:next(I2),
?assertEqual({20,20}, {K2, V2}),
?assertEqual(none, gb_trees:next(I3))
end
),
?_test(
begin
{K1, V1, I2} = gb_trees:next(lower_bound(2, Tree)),
?assertEqual({2,2}, {K1, V1}),
{K2, V2, _I3} = gb_trees:next(I2),
?assertEqual({4,4}, {K2, V2})
end
)
]
end
}.