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math library for metric sequences and binary arrays.

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mmath src mmath_comb.erl
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src/mmath_comb.erl 

%%%-------------------------------------------------------------------

%%% @author Heinz Nikolaus Gies <heinz@licenser.net>

%%% @copyright (C) 2016, Project-FiFo UG

%%% @doc

%%% Module that provide mmath functions that combine metrics.

%%% All functions take a list of realized metrics and return a single

%%% realized metric

%%% @end

%%% Created : 29 Apr 2016 by Heinz Nikolaus Gies <heinz@licenser.net>

%%%-------------------------------------------------------------------

-module(mmath_comb).

-include("mmath.hrl").



-ifdef(TEST).

-compile(export_all).

-endif.



-export([avg/1,

         sum/1

        %%,

         %%mul/1,

         %%merge/1,

         %%zip/2

        ]).





-define(APPNAME, mmath).

-define(LIBNAME, comb_nif).

-on_load(load_nif/0).

load_nif() ->

    SoName = case code:priv_dir(?APPNAME) of

                 {error, bad_name} ->

                     case filelib:is_dir(filename:join(["..", priv])) of

                         true ->

                             filename:join(["..", priv, ?LIBNAME]);

                         _ ->

                             filename:join([priv, ?LIBNAME])

                     end;

                 Dir ->

                     filename:join(Dir, ?LIBNAME)

             end,

    erlang:load_nif(SoName, 0).



%%--------------------------------------------------------------------

%% @doc

%% Creates a new dataset with each element being the sum of the

%% elements of the passed datasets.

%% @end

%%--------------------------------------------------------------------

sum([A, B]) ->

    sum(A, B);



sum([A, B, C]) ->

    sum(A, B, C);



sum(Es) ->

    rcomb(fun sum/2, fun sum/3, Es, []).











%%--------------------------------------------------------------------

%% @doc

%% Creates a new dataset with each element being the average (mean)

%% of the elements of the passed datasets.

%% @end

%%--------------------------------------------------------------------

avg(Es) ->

    mmath_trans:divide(sum(Es), length(Es)).



%%-------------------------------------------------------------------

%% Utility functions

%%-------------------------------------------------------------------



sum(_A, _B) ->

    exit(nif_library_not_loaded).



sum(_A, _B, _C) ->

    exit(nif_library_not_loaded).



%%--------------------------------------------------------------------

%% @doc

%% Combines a set of datasets with a given combinator function.

%% this requires the combinator to be associative!

%%--------------------------------------------------------------------



rcomb(F2, _F3, [A], [B]) ->

    F2(A, B);

rcomb(F2, F3, [], Acc) ->

    rcomb(F2, F3, Acc, []);

rcomb(_, _, [A], []) ->

    A;



rcomb(F2, F3, [A, B, C, D | R], Acc) ->

    rcomb(F2, F3, R, [F2(F2(A, B), F2(C, D)) | Acc]);



rcomb(F2, F3, [A, B, C | R], Acc) when is_function(F3) ->

    rcomb(F2, F3, R, [F3(A, B, C) | Acc]);



rcomb(F2, F3, [A, B | R], Acc) ->

    rcomb(F2, F3, R, [F2(A, B) | Acc]);



rcomb(F2, F3, [A], Acc) ->

    rcomb(F2, F3, [A | Acc], []).