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|---|---|---|
gaia |
true |
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|
Philip Chimento
Igalia, in partnership with Bloomberg
TC39 July 2023
- Presenting integer arithmetic change discussed in previous plenaries
- Also presenting two normative changes arising from implementor discussions
- All known discussions settled; these are the last expected changes
- Implementation continues (JSC, LibJS, SpiderMonkey, V8)
IETF standardization progress (#1450)
- IETF document currently in last call
- Some suggestions from area directors, and one complaint
- Complaint seems to be able to be handled with discussion
Integer math in durations (PR #2612) (1/3)
- Storage doesn't change; one f64-representable integer for each unit
- "90 minutes" preserved unless explicitly balanced to "1 hour 30"
- Calculations with time units (days* through nanoseconds) use "normalized form", s × 10⁹ + ns
- |s| ≤ max safe integer
- |ns| ≤ 999,999,999
- Can be implemented as: i96 ns; i64 s + i32 ns; f64 s + f64 ns
- At end of calculation, converted back to integer-per-unit for storage
*Why are days a time unit? We allow calculations without calendar, and assume 24-hour days in that case.
- Calendar units years, months, weeks, all limited to maxuint32
- |N| < 2³² for N = y, mon, w
- Why not maxint32? Because sign is common to all units
- Implementations can choose to store as u32 instead of f64
- Note, performing calculations with
relativeTodate can still fail- 2³²-1 years ≫ representable range
- With limits, calculations in loops no longer necessary
- Concern emerged in review of SpiderMonkey implementation
- Spec text encapsulates all 96-bit operations in AOs
- Can be changed editorially to explicitly be 64+32 or seconds+subseconds, if implementations prefer
- Few observable effects, but some durations no longer allowed
// e.g. no longer allowed:
Temporal.Duration.from({ seconds: Number.MAX_VALUE })
Temporal.Duration.from({
seconds: Number.MAX_SAFE_INTEGER,
milliseconds: 1000
})
// Maximum duration now accepted:
Temporal.Duration.from({