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%% @copyright Copyright (c) 2010 Mochi Media, Inc.
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%% @author David Reid <dreid@mochimedia.com>
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%%
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%% Permission is hereby granted, free of charge, to any person obtaining a
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%% copy of this software and associated documentation files (the "Software"),
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%% to deal in the Software without restriction, including without limitation
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%% the rights to use, copy, modify, merge, publish, distribute, sublicense,
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%% and/or sell copies of the Software, and to permit persons to whom the
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%% Software is furnished to do so, subject to the following conditions:
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%%
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%% The above copyright notice and this permission notice shall be included in
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%% all copies or substantial portions of the Software.
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%%
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%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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%% THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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%% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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%% DEALINGS IN THE SOFTWARE.
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%% @doc Utility functions for dealing with proplists.
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-module(mochilists).
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-author("David Reid <dreid@mochimedia.com>").
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-export([get_value/2, get_value/3, is_defined/2, set_default/2, set_defaults/2]).
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%% @spec set_default({Key::term(), Value::term()}, Proplist::list()) -> list()
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%%
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%% @doc Return new Proplist with {Key, Value} set if not is_defined(Key, Proplist).
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set_default({Key, Value}, Proplist) ->
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case is_defined(Key, Proplist) of
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true ->
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Proplist;
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false ->
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[{Key, Value} | Proplist]
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end.
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%% @spec set_defaults([{Key::term(), Value::term()}], Proplist::list()) -> list()
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%%
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%% @doc Return new Proplist with {Key, Value} set if not is_defined(Key, Proplist).
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set_defaults(DefaultProps, Proplist) ->
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lists:foldl(fun set_default/2, Proplist, DefaultProps).
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%% @spec is_defined(Key::term(), Proplist::list()) -> bool()
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%%
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%% @doc Returns true if Propist contains at least one entry associated
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%% with Key, otherwise false is returned.
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is_defined(Key, Proplist) ->
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lists:keyfind(Key, 1, Proplist) =/= false.
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%% @spec get_value(Key::term(), Proplist::list()) -> term() | undefined
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%%
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%% @doc Return the value of <code>Key</code> or undefined
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get_value(Key, Proplist) ->
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get_value(Key, Proplist, undefined).
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%% @spec get_value(Key::term(), Proplist::list(), Default::term()) -> term()
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%%
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%% @doc Return the value of <code>Key</code> or <code>Default</code>
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get_value(_Key, [], Default) ->
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Default;
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get_value(Key, Proplist, Default) ->
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case lists:keyfind(Key, 1, Proplist) of
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false ->
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Default;
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{Key, Value} ->
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Value
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end.
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%%
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%% Tests
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%%
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-ifdef(TEST).
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-include_lib("eunit/include/eunit.hrl").
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set_defaults_test() ->
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?assertEqual(
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[{k, v}],
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set_defaults([{k, v}], [])),
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?assertEqual(
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[{k, v}],
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set_defaults([{k, vee}], [{k, v}])),
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?assertEqual(
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lists:sort([{kay, vee}, {k, v}]),
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lists:sort(set_defaults([{k, vee}, {kay, vee}], [{k, v}]))),
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ok.
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set_default_test() ->
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?assertEqual(
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[{k, v}],
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set_default({k, v}, [])),
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?assertEqual(
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[{k, v}],
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set_default({k, vee}, [{k, v}])),
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ok.
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get_value_test() ->
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?assertEqual(
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undefined,
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get_value(foo, [])),
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?assertEqual(
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undefined,
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get_value(foo, [{bar, baz}])),
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?assertEqual(
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bar,
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get_value(foo, [{foo, bar}])),
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?assertEqual(
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default,
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get_value(foo, [], default)),
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?assertEqual(
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default,
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get_value(foo, [{bar, baz}], default)),
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?assertEqual(
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bar,
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get_value(foo, [{foo, bar}], default)),
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ok.
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-endif.
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