**Language: Erlang** Without using Erlang’s lists module functions, write a function concat/1, whose type is given by the following:
-spec concat(Lists :: [[T]]) -> [T].
The function concat takes a list of lists of elements (of some type T) and returns a list of the elements (of type T) formed by concatenating the inner lists together in order.
The following are examples written using the Erlang testing module. You can use the built-in ++ in your code, or any other helping functions. Run these tests by compiling your file and the
testing file, and then running concat_tests:main().
Example:
% $Id: concat_tests. erl, v 1.3 2015/03/12 13:50:59 leavens Exp leavens $
-module(concat_tests).
-import(testing,[dotests/2,eqTest/3 ]).
-export([main/0, tests/1]).
main() ->
compile:file(concat),
dotests("concat_tests $Revision: 1.3 $", tests(fun concat:concat/1)).
-spec tests(CFun :: fun(([[T]]) -> [T])) -> testing:testCase([atom()]).
tests(CFun) ->
[eqTest(CFun([]), "==", []),
eqTest(CFun([[]]), "==", []),
eqTest(CFun([[fee], [fie], [fo], [fum]]), "==", [fee, fie, fo, fum]),
eqTest(CFun([[], [hmm], [], [okay]]), "==", [hmm, okay]),
eqTest(CFun([[keep], [ancient, lands], [your, storied, pomp], [cries, she]]),
"==", [keep, ancient, lands, your, storied, pomp, cries, she]),
eqTest(CFun([[four, score, nd, seven], [years, ago], [our, ancestors],
[brought, forth, on, this, continent], [a, new, nation]]),
"==", [four, score, nd, seven, years, ago, our, ancestors,
brought, forth, on, this, continent, a, new, nation]),
eqTest(CFun([[[more],[nested]], [[than],[before]]]),
"==", [[more], [nested], [than], [before]])
].