a convolution program.

fir.erl

-module(fir).
-export([convolute/2]).

convolute_acc(F, G, Acc) when length(F) =:= 2 * length(G) - 1 ->
    lists:reverse(Acc);
convolute_acc(F, G, Acc) ->
    V = lists:sum(lists:map(fun({A, B}) -> A * B end,
                            lists:zip(lists:sublist(F, length(G)), G))),
    convolute_acc(tl(F), G, [V | Acc]).

convolute(F, G) ->
    F2 = lists:append([lists:duplicate(length(G) - 1, 0.0), F, lists:duplicate(length(G), 0.0)]),
    convolute_acc(F2, lists:reverse(G), []).