Allow float keywords in to_timeout/1.

[christhekeele]

Per core discussion, I ran into another situation with a dynamically-calculated rate limit from an API response (in fractional minutes), and thought I would proffer an implementation.

While floats are not allowed in Durations, it makes sense to me that since the purpose of to_timeout/1 is not to construct a Duration, a general-purpose Kernel function should be made more flexible. Duration and simple numeric arguments still require integers, to encourage thinking of timeouts on millisecond timescales.

I understand the mailing list discussion did not end with a [👍 PRs welcome], so feel free to close if the argument for this form is not sufficiently persuasive.

[josevalim]

Thank you but I am not comfortable with supporting floats, given the imprecision from operations and the fact timeouts in Erlang are only integer too. I understand the application specific concerns but then I suggest those be tackled by the application. :)

PS: if we were to merge it, then I would suggest rounding up, as timeout guarantees “at least”. But as per above, I wouldn’t go ahead with this feature.

[christhekeele]

Your reservations make sense! This PR does in fact round to always get integers, and always rounds up, to eat the imprecisions, FWIW. See:

Fractional milliseconds are rounded upwards with ceil/1 to ensure the timeout exceeds the requested value.

[josevalim]

We won't go ahead with this, per above. :)

This PR does in fact round to always get integers, and always rounds up, to eat the imprecisions

Ah, perfect. I got confused with the mailing message then!