AltME: Ren - Time & Duration


"Storing in memory each time component as 32-bit values is obviously a waste of space, so this is not satisfying."
This, I would say, is not Ren's concern, and somewhat akin to saying ints should be 16 bits.
But I think we're largely on the same page otherwise. :-)
I started a Ren parser, and if we're OK saying that the time part of a date, and timezone as well, are limited, then all we have to fight about is standalone time values (relative time). Because if I can only say 23:59:59, maximum, not only do I lose meaning, but I'm limiting the relative range I can talk about. Strictly speaking, I can't even say 24:00, right?.
This does add some complexity, though it's not bad as long as we require a fixed number of digits in each segment.
Note that my implied-string is separate from a quoted or braced string. No quotes. The one thing I don't cover yet is tags, which is tougher. It's pending question about whether they can be considered just another kind of string, and can we also present parens as just another list synatx along with square brackets. I was thinking of leaving them out of v1, having a page of proposals, and adding them later.
"This, I would say, is not Ren's concern, and somewhat akin to saying ints should be 16 bits."
Well, I understand your perspective, but you should realize that even R2 and R3 could not support Ren as-is if you stick to 32-bit time components.
A special case could be made for 24:00 value, though, I think that it is not worse it. If you want to represent just hours, you can use integers for that.
worse => worth
Timezones are another tricky area. I believe the range of timezones is -12:00 to + 14:00. Most timezone are either 0 minutes or 30 minutes. However, there is Chatham Islands (New Zealand) at +12"45, Eucla (Australia) +8:45, Nepal +5:45. None at 15 minutes past the hour though.
Tom Scott has a nice video about this subject.
There are always going to be limits in implementations, no doubt. But R2 loads 99999:99999999:999.999 just fine. R2 also does some crazy things with signed times and overflow, but that hasn't stopped it from being useful 99.9999999% of the time(s). ;-)
Also, R3 gives a different result than R2 for the above time value.
A compromise would be to set a limit that could be represented in most langs with reasonable efficiency. And look at it the other way. How many systems use epoch seconds, ms, or 100 ns as time units? We need to be able to represent those, correct? If not, you end up with integers, as you say, which provide no meaning. We effectively cripple time.
I don't worry that people will generate huge values from other systems, because those have their own limits as well, so the chances of someone generating a time like the above is virtually nil. My concern is security and opening doors for overflow attacks and such.
Again, I'm OK with limits for absolute time values, as in date-time. Timezones are an issue, which are a constrained relative time, and I'm good with limiting those as well. Right now my parse rules allow any hour 00-23, which we can address limits of separately if we want.
    hour=: [
        [[#"0" | #"1"] digit=]
        | [#"2" [#"0" | #"1" | #"2" | #"3"]]
    timezone=: ["Z" | sign= hour= #":" ["00" | "15" | "30"| "45"]]
I thought there was something at a 0:15 offset, but it's easy to remove.
In order to allow large relative times to be represented, we either need to allow times to contain large segment values and/or extend the notion of time to include duration as well, with a new notation.
Do not limit timezone at 15 minutes. Timezones should have at least 1 minute resolution.
Even though they aren't recognized as valid? Noting that I agree with you :-), why so?
"Valid" meaning "used in the world today".
The reason I'm OK with the 0:15 limitation in v1 is that we can later relax the constraint without breaking data. In general, I want to let people express their data, even if it may not make sense to us right now. We say what a type of value looks like, but impose few semantic restrictions.
Timezones are crazy stuff, there were not quarter hour based timezones in the past and there's no reason to not expect them in the future.
TZ - Agreed, it has to be treated as  filter/list that will change, and piss us all off.
(Windows changed the defaults between Windows 7 and 8,  names of cities also change, and so does the geographical location of the splits)
Time & Duration is a big topic to handle.   IEEE should have a library for this.  Excel SUCKS for this of note
+1 for 0:01 timezone support.
A little research, for comparison. (long message)
A Duration represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years.
ParseDuration parses a duration string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
  func Date
    func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time
    Date returns the Time corresponding to yyyy-mm-dd hh:mm:ss + nsec nanoseconds in the appropriate zone for that time in the given location. The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1.
For example, "P3Y6M4DT12H30M5S" represents a duration of "three years, six months, four days, twelve hours, thirty minutes, and five seconds".
To resolve ambiguity, "P1M" is a one-month duration and "PT1M" is a one-minute duration (note the time designator, T, that precedes the time value). The smallest value used may also have a decimal fraction, as in "P0.5Y" to indicate half a year. This decimal fraction may be specified with either a comma or a full stop, as in "P0,5Y" or "P0.5Y". The standard does not prohibit date and time values in a duration representation from exceeding their "carry over points" except as noted below. Thus, "PT36H" could be used as well as "P1DT12H" for representing the same duration.
A Duration object is measured in seconds or nanoseconds and does not use date-based constructs such as years, months, and days, though the class provides methods that convert to days, hours, and minutes. A Duration can have a negative value
To define an amount of time with date-based values (years, months, days), use the Period class...The total period of time is represented by all three units together: months, days, and years.
In versions prior to Ruby 1.9 and on many systems Time is represented as a 32-bit signed value describing the number of seconds since January 1, 1970 UTC, a thin wrapper around a POSIX-standard time_t value, and is bounded
Since Ruby 1.9.2, Time implementation uses a signed 63 bit integer, Bignum or Rational. The integer is a number of nanoseconds since the Epoch which can represent 1823-11-12 to 2116-02-20. When Bignum or Rational is used (before 1823, after 2116, under nanosecond), Time works slower as when integer is used.
Duration object is stored as seconds.
A TimeSpan object represents a time interval (duration of time or elapsed time) that is measured as a positive or negative number of days, hours, minutes, seconds, and fractions of a second. The TimeSpan structure can also be used to represent the time of day, but only if the time is unrelated to a particular date.
The largest unit of time that the TimeSpan structure uses to measure duration is a day. Time intervals are measured in days for consistency, because the number of days in larger units of time, such as months and years, varies.
The value of a TimeSpan object is the number of ticks that equal the represented time interval. A tick is equal to 100 nanoseconds, or one ten-millionth of a second. The value of a TimeSpan object can range from TimeSpan.MinValue (The string representation of this value is negative 10675199.02:48:05.4775808, or slightly more than negative 10,675,199 days.) to TimeSpan.MaxValue (The string representation of this value is positive 10675199.02:48:05.4775807, or slightly more than 10,675,199 days.).
TimeDelta - Only days, seconds and microseconds are stored internally...Note that normalization of negative values may be surprising at first.
- The most negative timedelta object, timedelta(-999999999).
- The most positive timedelta object, timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999).
- The smallest possible difference between non-equal timedelta objects, timedelta(microseconds=1).
- seconds: Between 0 and 86399 inclusive
Just for fun:
- Planck time: 0:0:0.0000000000000000000000000000000000000000000054
- Age of universe: 0:0:432'000'000'000'000'000
I know this is a long discussion but, it's such an important element, I think it's worth it.
- I don't like the ISO8601/iCal/Go format for durations. e.g., "P3Y6M4DT12H30M5S"
- I DO want a dialect or lexical that lets us express units, but now is not the time, as Doc says.
- I think we should support large relative date-time values.

Last message posted 299 weeks ago.