On Mon, Jul 20, 2020 at 01:08:57PM -0700, tim Rowledge wrote:
> Time >addSeconds: completely ignores the nanos ivar value and so
> Time now -> (say)  12:51:47.418205 pm
> send that #addSeconds: 2 -> 12:51:49 pm
> 
> Which is incorrect. Actually *fixing* it seems to be a bit more complex
> than just "add the nanoseconds stuff".
> 
> Should #asSeconds be truncating the seconds and ignoring the nanoseconds?
> That's also an issue for #addTime: and #subtractTime: (wait, no #subtractSeconds: ?)
> 
> Chronology-afficonados assemble!
>

I'm a bit late following up on this, but I'm working on some unit tests
and a fix to be submitted to inbox soon.

I took a look at Squeak 3.6 (prior to the introduction of the Chronology
package). I was expecting that Time instances had originally assumed the
use of whole seconds, but to my pleasant surprise, it is not so.

Here is what I see in Squeak 3.6, which looks entirely right to me (note
that I am intentionally using a completely inappropriate Float value to
illustrate the point):

  t1 := Time fromSeconds: Float pi. "==> 12:00:03.141592653589793 am"
  t2 := t1 addSeconds: Float pi. "==> 12:00:06.283185307179586 am"
  t1 seconds. "==> 3.141592653589793"
  t1 asSeconds. "==> 3.141592653589793"
  t2 seconds. "==> 6.283185307179586"
  t2 asSeconds. "==> .283185307179586"
  t2 asSeconds - t1 asSeconds. "==> 3.141592653589793"

And here is what I see in trunk today, which is clearly broken:

  t1 := Time fromSeconds: Float pi. "==> 12:00:03.141592653 am"
  t2 := t1 addSeconds: Float pi. "==> 12:00:06.141592654 am"
  t1 seconds. "==> 3"
  t1 nanoSecond. "==> 141592653"
  t1 asSeconds. "==> 3"
  t1 asNanoSeconds. "==> 3141592653"
  t2 seconds. "==> 6"
  t2 nanoSecond. "==> 141592654"
  t2 asSeconds. "==> 6"
  t2 asNanoSeconds. "==> 6141592654"
  t2 asSeconds - t1 asSeconds. "==> 3"
  t2 asNanoSeconds - t1 asNanoSeconds. "==> 3000000001"

By fixing #addSeconds to respect the nanos ivar, we will have
something more like this:

  t1 := Time fromSeconds: Float pi. "==> 12:00:03.141592653 am"
  t2 := t1 addSeconds: Float pi. "==> 12:00:06.283185307 am"
  t1 seconds. "==> 3"
  t1 nanoSecond. "==> 141592653"
  t1 asSeconds. "==> 3"
  t1 asNanoSeconds. "==> 3141592653"
  t2 seconds. "==> 6"
  t2 nanoSecond. "==> 283185307"
  t2 asSeconds. "==> 6"
  t2 asNanoSeconds. "==> 6283185307"
  t2 asSeconds - t1 asSeconds. "==> 3"
  t2 asNanoSeconds - t1 asNanoSeconds.  "==> 3141592654"

That will still leave us with inconsistent behavior with respect to
#asSeconds, but that is probably a separate topic, and best checked
against the behavior of other Smalltalk dialects for compatibility.

Dave