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120 lines
3.6 KiB
120 lines
3.6 KiB
%% @doc Built in operators.
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-module(glc_ops).
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-export([
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lt/2,
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eq/2,
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gt/2,
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wc/1
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]).
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-export([
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all/1,
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any/1,
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null/1,
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with/2
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]).
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-export([
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union/1
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]).
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-type op() ::
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{atom(), '<', term()} |
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{atom(), '=', term()} |
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{atom(), '>', term()} |
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{atom(), '*'} |
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{any, [op(), ...]} |
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{all, [op(), ...]} |
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{null, true|false}.
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-export_type([op/0]).
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%% @doc Test that a field value is less than a term.
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-spec lt(Key::atom(), Term::term()) -> {Key::atom(), '<', Term::term()}.
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lt(Key, Term) when is_atom(Key) ->
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{Key, '<', Term};
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lt(Key, Term) ->
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erlang:error(badarg, [Key, Term]).
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%% @doc Test that a field value is equal to a term.
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-spec eq(Key::atom(), Term::term()) -> {Key::atom(), '=', Term::term()}.
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eq(Key, Term) when is_atom(Key) ->
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{Key, '=', Term};
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eq(Key, Term) ->
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erlang:error(badarg, [Key, Term]).
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%% @doc Test that a field value is greater than a term.
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-spec gt(Key::atom(), Term::term()) -> {Key::atom(), '>', Term::term()}.
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gt(Key, Term) when is_atom(Key) ->
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{Key, '>', Term};
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gt(Key, Term) ->
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erlang:error(badarg, [Key, Term]).
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%% @doc Test that a field value is exists.
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-spec wc(Key::atom()) -> {Key::atom(), '*'}.
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wc(Key) when is_atom(Key) ->
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{Key, '*'};
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wc(Key) ->
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erlang:error(badarg, [Key]).
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%% @doc Filter the input using multiple filters.
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%%
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%% For an input to be considered valid output the all filters specified
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%% in the list must hold for the input event. The list is expected to
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%% be a non-empty list. If the list of filters is an empty list a `badarg'
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%% error will be thrown.
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-spec all(Conds::nonempty_maybe_improper_list()) -> {all, Conds::nonempty_maybe_improper_list()}.
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all([_|_]=Conds) ->
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{all, Conds};
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all(Other) ->
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erlang:error(badarg, [Other]).
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%% @doc Filter the input using one of multiple filters.
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%%
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%% For an input to be considered valid output on of the filters specified
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%% in the list must hold for the input event. The list is expected to be
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%% a non-empty list. If the list of filters is an empty list a `badarg'
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%% error will be thrown.
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-spec any(Conds::nonempty_maybe_improper_list()) -> {any, Conds::nonempty_maybe_improper_list()}.
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any([_|_]=Conds) ->
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{any, Conds};
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any(Other) ->
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erlang:error(badarg, [Other]).
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%% @doc Always return `true' or `false'.
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-spec null(Result::boolean()) -> {null, Result::boolean()} | no_return().
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null(Result) when is_boolean(Result) ->
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{null, Result};
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null(Result) ->
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erlang:error(badarg, [Result]).
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%% @doc Apply a function to each output of a query.
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%%
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%% Updating the output action of a query finalizes it. Attempting
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%% to use a finalized query to construct a new query will result
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%% in a `badarg' error.
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-spec with(Query::op(), Fun::fun((gre:event()) -> term())) ->
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{with, Query::op(), Fun::fun((gre:event()) -> term())} | no_return().
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with(Query, Fun) when is_function(Fun, 1) ->
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{with, Query, Fun};
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with(Query, Fun) ->
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erlang:error(badarg, [Query, Fun]).
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%% @doc Return a union of multiple queries.
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%%
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%% The union of multiple queries is the equivalent of executing multiple
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%% queries separately on the same input event. The advantage is that filter
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%% conditions that are common to all or some of the queries only need to
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%% be tested once.
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%%
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%% All queries are expected to be valid and have an output action other
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%% than the default which is `output'. If these expectations don't hold
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%% a `badarg' error will be thrown.
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-spec union(Queries::[op()]) -> {union, Queries::[op()]} | no_return().
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union(Queries) ->
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case [Query || Query <- Queries, glc_lib:onoutput(Query) =:= output] of
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[] -> {union, Queries};
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[_|_] -> erlang:error(badarg, [Queries])
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end.
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