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104 linhas
3.2 KiB
104 linhas
3.2 KiB
%% Copyright (c) 2012, Magnus Klaar <klaar@ninenines.eu>
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%%
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%% Permission to use, copy, modify, and/or distribute this software for any
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%% purpose with or without fee is hereby granted, provided that the above
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%% copyright notice and this permission notice appear in all copies.
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%%
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%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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%% @doc Accessor function for goldrush event terms.
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-module(gre).
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-export([
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make/2,
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has/2,
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fetch/2,
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append/2,
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merge/2,
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find/2,
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keys/1,
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pairs/1
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]).
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-type event() :: {list, [{atom(), term()}]}.
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-export_type([event/0]).
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%% @doc Construct an event term.
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-spec make(term(), [list]) -> event().
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make(Term, [Type]) ->
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{Type, Term}.
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%% @doc Check if a field exists in an event.
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-spec has(atom(), event()) -> boolean().
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has(Key, {list, List}) ->
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lists:keymember(Key, 1, List).
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-spec append(term(), event()) -> event().
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append(KeyVal, {list, List}) ->
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{list, [KeyVal|List]}.
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-spec merge(event(), event()) -> event().
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merge({list, AList}, {list, BList}) ->
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{list, lists:merge(AList, BList)}.
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%% @doc Get the value of a field in an event.
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%% The field is expected to exist in the event.
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-spec fetch(atom(), event()) -> term().
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fetch(Key, {list, List}=Event) ->
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case lists:keyfind(Key, 1, List) of
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{_, Value} -> Value;
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false -> erlang:error(badarg, [Key, Event])
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end.
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%% @doc Find the value of a field in an event.
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%% This is equivalent to testing if a field exists using {@link has/2}
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%% before accessing the value of the field using {@link fetch/2}.
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-spec find(atom(), event()) -> {true, term()} | false.
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find(Key, {list, List}) ->
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case lists:keyfind(Key, 1, List) of
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{_, Value} -> {true, Value};
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false -> false
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end.
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%% @doc Get the names of all fields in an event.
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-spec keys(event()) -> [atom()].
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keys({list, List}) ->
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kv_keys_(List).
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%% @private Get the names of all fields in a key-value list.
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-spec kv_keys_([{atom(), term()}]) -> [atom()].
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kv_keys_([{Key, _}|T]) ->
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[Key|kv_keys_(T)];
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kv_keys_([]) ->
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[].
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%% @doc Get the name and value of all fields in an event.
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-spec pairs(event()) -> [{atom(), term()}].
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pairs({list, List}) ->
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lists:sort(List).
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-ifdef(TEST).
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-include_lib("eunit/include/eunit.hrl").
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gre_test_() ->
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[?_assert(gre:has(a, gre:make([{a,1}], [list]))),
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?_assertNot(gre:has(b, gre:make([{a,1}], [list]))),
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?_assertEqual(1, gre:fetch(a, gre:make([{a,1}], [list]))),
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?_assertError(badarg, gre:fetch(a, gre:make([], [list]))),
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?_assertEqual([], gre:keys(gre:make([], [list]))),
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?_assertEqual([a], gre:keys(gre:make([{a,1}], [list]))),
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?_assertEqual([a,b], gre:keys(gre:make([{a,1},{b,2}], [list]))),
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?_assertEqual([{a,1},{b,2}], gre:pairs(gre:make([{b,2},{a,1}], [list])))
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].
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-endif.
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