Module kinds 

Haystack type system — the Kind enum and its 15 scalar types.

Every value in the Haystack data model is represented as a Kind variant:

Variant	Rust Type	Zinc Example
Marker	Marker	M
NA	NA	NA
Remove	Remove	R
Bool(bool)	bool	T / F
Number(Number)	Number	72°F, 100kW
Str(String)	String	"hello"
Ref(HRef)	HRef	@site-1 "Main Site"
Uri(Uri)	Uri	`http://example.com`
Date(NaiveDate)	chrono::NaiveDate	2024-01-15
Time(NaiveTime)	chrono::NaiveTime	13:30:00
DateTime(HDateTime)	HDateTime	2024-01-15T13:30:00-05:00 New_York
Coord(Coord)	Coord	C(37.55,-77.45)
Symbol(Symbol)	Symbol	^hot-water
XStr(XStr)	XStr	Type("value")
List(HList)	HList	[1, 2, 3]
Dict(Box<HDict>)	HDict	{dis:"Room" area:100}
Grid(Box<HGrid>)	HGrid	Nested grid

The [units] submodule provides a database of standard Haystack units with lookup by name (unit_for) or symbol (units_by_symbol).

Structs

Coord

A geographic coordinate represented as latitude and longitude in decimal degrees.

HDateTime

Timezone-aware datetime with Haystack city-based timezone name.

HRef

Haystack Ref — an entity reference.

Marker

Marker tag — boolean presence indicator. In Zinc: M. In JSON: {"_kind": "marker"}.

NA

Not Available — missing or invalid data sentinel. In Zinc: NA. In JSON: {"_kind": "na"}.

Number

Haystack Number — a 64-bit float with optional unit string.

Remove

Remove — tag removal in diff/update operations. In Zinc: R. In JSON: {"_kind": "remove"}.

Symbol

Reference to a def/tag definition name. Zinc: ^hot-water

Unit

A Haystack unit definition.

Uri

A Haystack URI value wrapping an arbitrary string.

XStr

Extended typed string — vendor-specific scalar. Zinc: Color("red")

Enums

Kind

The central Haystack value type. Every tag value is a Kind.

Functions

tz_for

Resolve a Haystack timezone name to an IANA identifier.

tz_map

Get the full timezone map.

unit_for

Look up a unit by name or symbol.

units_by_name

Get all units indexed by name.

units_by_symbol

Get all units indexed by symbol.