Duration & Instant

Duration and Instant are time-related types with special literal and operator support.

Key ideas:

• Duration represents a signed time span.
• Instant represents a signed point-in-time on a monotonic timeline (an opaque epoch chosen by the runtime).
• Duration literals represent time spans with unit suffixes and are converted into integral ticks.
• Operators cover arithmetic, comparisons, and construction from scalars.

Representation#

In Silk:

• Duration is represented as a signed 64-bit integer count of nanoseconds.
• Instant is represented as a signed 64-bit integer count of nanoseconds since a monotonic, runtime-defined origin.

These are distinct Silk types in the type system, but share the same underlying scalar representation (i64) at the IR and native ABI layers.

Operators#

Supported operator subset:

• Duration + Duration -> Duration

• Duration - Duration -> Duration

• -Duration -> Duration

• Instant + Duration -> Instant

• Duration + Instant -> Instant

• Instant - Duration -> Instant

• Instant - Instant -> Duration

• Comparisons (==, !=, <, <=, >, >=) are supported for:

• Duration vs Duration

• Instant vs Instant

Other arithmetic (*, /, %) and bitwise operators are not defined for time types in the Supported forms.

Overflow#

Arithmetic uses the same deterministic wrapping behavior as the underlying i64 operations in the current back-end subset (two’s complement wraparound).

Notes#

At maturity, this document will be expanded to fully specify:

• duration/instant division semantics and rounding rules,
• checked/saturating variants exposed by the standard library,
• the precise relationship between Instant and the platform clock APIs,
• and FFI-safe conversions and APIs in std::temporal.

Compiler requirements:

• Implement type-checking and lowering for the operator subset above.
• Implement duration literal parsing as specified in literals duration.
• Integrate with std::temporal in the standard library.