Erlang: Adding together tuples?

Question

I tried doing this to make a new date 90 seconds ahead of the current system time:

12> {{00,00,00},{00,01,30}}+erlang:localtime().
** exception error: an error occurred when evaluating an arithmetic expression
     in operator  +/2
        called as {{0,0,0},{0,1,30}} + {{2013,3,8},{6,3,33}}

Are there any easy methods for doing this?

Answer 1

You can't just add tuples in erlang. You could add the individual integers inside the tuples but to manipulate time, you should use the calendar module (docs):

1> Added = calendar:datetime_to_gregorian_seconds(calendar:local_time()) + 90.
63529954043
2> calendar:gregorian_seconds_to_datetime(Added).
{{2013,3,8},{9,27,23}}