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Descriptor Reference

Translated from the canonical Japanese page reference/README.md. The source_sha above records the source revision; a consistency check flags this page when the Japanese original changes.

Explains Kairos’s descriptors (operators, window-generating words, literals), one word per file. The norm is the language specification ../spec/ (this book is the explanatory layer — the same division of roles by which stdlib/ carries Gregorian). The index of terms is ../spec/50-glossary.md.

Conventions for runnable examples (doctest)

Of the code examples in this book, those in ``kairos ` fences are execution-verified against the reference implementation (../../impl/) (impl/test/doctest.test.ts). The doctest runs on the Japanese source pages; a consistency check keeps this mirror’s blocks identical to them (code lines and the # eval:/#=>/#~> lines — comments may be translated), so the guarantee carries over. The same conventions extend to the explanatory pages of ../stdlib/.

• The # eval: FROM..TO line in a block is the evaluation range ([FROM, TO)). The optional postfix tz: Zone (e.g. # eval: 2026-03-06..2026-03-10 tz: America/New_York) overrides the execution/display tz (default Asia/Tokyo) — so that multi-TZ examples can write their expected values in the premise’s wall clock. Make tz: match the example premise’s tz (do not attach it to @JP = Asia/Tokyo blocks; a mismatch is not checked — only the endpoints of the evaluation range and the display move to the execution tz’s side).
• #=> lines are the expected values (the result of the last body expression; whitespace-separated, multiple lines allowed). Absence of the line is a claim of “zero points (an empty sequence)” (symmetric with the #~> default — empty-table (ADR-45)-class examples assert emptiness by writing no #=>. A bare #=> line is not read as an expectation, so it is not written). Both are Kairos line comments, so the source stays valid as-is. Points at exact midnight print as the date only (the same notation as day-granularity points). Sub-second fractions are truncated in display (a point at …T00:39:35.244 prints as …T00:39:35; point identity is kept at ms precision — a rounding of display, not of value).
• #~> lines are the expected annotations and warnings (the last body expression’s interval annotations = the same canonical one-line form as the CLI’s ⚠ lines, 範囲外 FROM..TO（源 covering …[, asof …]）; warnings are prefixed 警告: . Matched in order of appearance). Translator’s note: annotation expectation lines (#~>) reproduce the reference implementation’s canonical one-line output, which is currently Japanese; they are kept verbatim in this English mirror.
• A # resolve: bindingName = dates date… covering: … asof: … line is the resolver fixture for external (the data is written inside the document, so verification is self-contained. The first stage supports the dates wire only). Absence of the lines is a claim of “zero annotations, zero warnings” — the degeneration of out-of-coverage provenance (ADR-37’s “degenerates but is observable”) is explicit in runnable examples too and never passes silently (sealing the blind spot where, even when horizon demotion leaves a year-typo-class mistake at a mere warning, a doctest matching only date sequences would let it slide). The coverage summary is a permanently displayed monitoring surface and is therefore not matched.
• Blocks that use @JP get the standard premises automatically prepended: the calendar entity premise TSE { …; nonWorking = satSun | holidays2026 } (the actual holidays of 2026 = 18 days, including the substitute holiday 5/6 and the citizens’ holiday 9/22) and premise JP { calendar-system: Gregorian; calendar: TSE; tz: "Asia/Tokyo"; wkst: Mon }, plus the bindings holidays2026 and satSun. bizDay is the standard derivation from calendar: TSE (ADR-35 — the doctest suite as a whole doubles as execution verification of entity-mediated derivation).
• ` ```text ` fences are explanatory (not executed).

Index

Category	Word	One line
Generator	everyDay	streams every day of the in-scope calendar system
Generator	everyInstant	every point of the continuous base (used with strideBy)
Window	within	partition-type window (bundle by window name)
Window	segmentBy	interval-sequence-type window (cut at markers)
Selector	first / nth / last	the Nth, first, and last within a window
Point transform	roll	nudge invalid points to valid ones
Point transform	shift	move by n units
Point transform	snapTo	map to the first point of the containing window (floor)
Point transform	rebase	date-label-preserving re-anchoring (cross-tz same date)
Filter	filter	thin by predicate (premise predicate / value-expression predicate)
Stride	stride	“every n” points of the input (boundary-ignoring, continuous)
Stride	strideBy	step by width, “every w”
Combinator	\| & \	union, intersection, difference, and the cascade
Projection	ordinalIn	the ordinal of the unit window within the frame window (1-based)
Projection	epochOrdinal	running ordinal from the epoch (0-based)
Projection	coincides	window-membership predicate (is a point of S in d’s window)
Window-generating word	grid	uniform partition of the continuous axis (the calendar’s atoms)
Window-generating word	span	variable aggregation of unit sequences (bottom-up)
Window-generating word	split	variable division of a parent window (dependent windows)
Window-generating word	cycle	parallel repeating labels (labels, not windows)
Derivation	with	override an existing premise’s public words
Derivation	rephase	sugar shifting window cut points by a unit (re-phase; formerly the placeholder shiftBoundary)
Literal	table literal	stream constant of an instant sequence (covering:/labels:)
Supply	external	external supply declaration (a table literal resolved at run time. ADR-46)
Calendar entity	nonWorking	the entity’s reserved public word and the bizDay standard derivation (ADR-35)
Calendar entity	isOpen	the business-hours supply convention sessionOpens/sessionCloses and the standard derivations bizOpen/bizClose/isOpen (ADR-41)

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