Mean Length Of Fasta Sequences

Erlang special golfing 213 chars version:

-module(g).
-export([s/0]).
s()->open_port({fd,0,1},[in,binary,{line,256}]),r(0,0),halt().
r(C,L)->receive{_,{_,{_,<<$>:8,_/binary>>}}}->r(C+1,L);{_,{_,{_,Line}}}->r(C,L+size(Line));_->io:format("~p~n",[L/C])end.

Readable but reliable version:

-module(g).
-export([s/0]).
s()->
  P = open_port({fd, 0, 1}, [in, binary, {line, 256}]),
  r(P, 0, 0),
  halt().
r(P, C, L) ->
  receive
    {P, {data, {eol, <<$>:8, _/binary>>}}} ->
      r(P, C+1, L);
    {P, {data, {eol, Line}}} ->
      r(P, C, L + size(Line));
    {'EXIT', P, normal} ->
      io:format("~p~n",[L/C]);
    X -> io:format("Unexpected: ~p~n",[X]),exit(bad_data)
  end.

Compile:

$ erl -smp disable -noinput -mode minimal -boot start_clean -s erl_compile compile_cmdline @cwd /home/hynek/Download @option native @option '{hipe, [o3]}' @files g.erl

Invocation:

$ time erl -smp disable -noshell -mode minimal -boot start_clean -noinput -s g s<uniprot_sprot.fasta 
352.6697028442464

real    0m3.241s
user    0m3.060s
sys     0m0.124s