compatibility with erlang 18

[benoitc]

add compatibility with erlang 18 and sup. use erlang:timestamp() instead of erlang:now()

[uwiger]

If called on an older erlang version, this will result in a call to code_server. Better to check using erlang:is_builtin(erlang, timestamp, 0). Example, using R16B03:

5> try erlang:timestamp() catch error:undef -> undefined end.
(<0.41.0>) call code_server:call(code_server,{ensure_loaded,erlang})
(<0.41.0>) returned from code_server:call/2 -> {module,erlang}
undefined
6> erlang:is_builtin(erlang,timestamp,0).
false
7> erlang:is_builtin(erlang,now,0).      
true

[benoitc]

@uwiger The try/catch was mostly here to speed the usage, at least on erlang 18. Anyway I made the change you suggested. To skip the need to test the module each time it needed I create at compile time a module named jobs_time_compat. Let me know what you think about it.

[uwiger]

I think generating code is overkill for this particular problem. I would suggest going with an is_builtin() check, and the next optimization might be to generate a millisecond-timestamp directly, rather than a now()-tuple.

[uwiger]

... to clarify, with "next optimization", I didn't mean this PR. :)

[benoitc]

@uwiger just pushed a simpler version. Should be good now :)

[uwiger]

Did you push jobs_time_compat.erl?

[uwiger]

never mind - forgot to refresh.

[benoitc]

? mm no I put time_compat/0 in jobs_lib right now

[benoitc]

heh np :)

[uwiger]

thanks!