A Kotlin Multiplatform library of strongly-typed, shareable data types — money and currency, locales, coordinates and telemetry, GeoJSON geometry, RFC-compliant identifiers, and arbitrary-precision math. It exists because KMP projects kept redefining the same types incompatibly; these are the shared ones, with no platform-specific API leaking through.

Targets: Android, JVM, iOS, JS, Wasm and Linux.

Published to Maven Central as io.github.aughtone:types.

// build.gradle.kts
implementation("io.github.aughtone:types:3.4.0")

Or through a version catalog:

# gradle/libs.versions.toml
[versions]
aughtone-types = "3.4.0"

[libraries]
aughtone-types = { module = "io.github.aughtone:types", version.ref = "aughtone-types" }

// build.gradle.kts
implementation(libs.aughtone.types)

[!IMPORTANT] v3.4.0 Outcome.Error renamed: The failure case of Outcome is now Outcome.Failure, and the factory is Outcome.failure(...). The old names still compile as deprecated aliases and will be removed in 4.0.0. Outcome$Error no longer exists as a class, so upgrading from 3.3.0 needs a clean and rebuild rather than a code change.

v3.3.0 Locale Display Names: Eleven locale displayName values are corrected — renamed countries (Czechia, North Macedonia, Türkiye), incomplete or abbreviated country names, and dated language exonyms (Farsi → Persian, Azeri → Azerbaijani). No API changed, but snapshot tests and cached UI strings holding the old names will need updating. See the changelog for the full table.

v3.2.0 Behavioral Fixes: Still worth reading if you are coming from 3.1.x — that release corrected long-standing bugs whose output or validation changes for existing code. UrlEncoder.encode is now true RFC 3986 percent-encoding — use encodeFormData for the previous application/x-www-form-urlencoded behavior. Url/Uri/Urn/GeoUri string output is now well-formed, and Urn/GeoUri construction now rejects invalid input. Critical arbitrary-precision fixes also land in BigInteger/BigDecimal division and BankersValue. See the changelog for the full list.

v3.0.0 Breaking Change: All GeoJSON geometry types (e.g., Point, Polygon) have been renamed with a Geo prefix (e.g., GeoPoint, GeoPolygon). Money now uses BigDecimal for its internal value to support sub-minor units, and Telemetry has moved to the quantitative package.

• 📖 Developer Guide: Building, testing, publishing.
• ⚖️ Architecture Decision Records: Why the library is shaped this way, and what was rejected.
• 📜 Changelog: History of changes and release notes.
• 🗺️ How the docs work: The whole system — knowledge in docs/knowledge/, work in Issues.

• Locales: Locale.current or localeFor("fr-CH").
• Money: Money(12.50, Currency.Usd) or Money(BigDecimal("1.23456"), Currency.Eur).
• Telemetry: Telemetry(coords, speed = 2.5.mps, azimuth = 90.degrees).

• Distance: 100.meters or 5.kilometers.
• Units: UnitOfMeasure.Litre.symbol ("L"), MetricPrefix.Kilo.

• Identifiers: Url("https://pkg.dev"), Urn("urn:uuid:...").
• Geo: GeoUri(45.5, -122.6) (RFC 5870).

• Arbitrary Precision: BigInteger("999999999999999999999999") or BigDecimal("123.456").
• Rounding: BigDecimal("1.255").setScale(2, RoundingMode.HALF_EVEN) -> 1.26.

• Outcome: runOutcome { parse(input) } returns Outcome.Success or Outcome.Failure; when over the two, or use fold, map, recover, dataOrElse.
• Unlike kotlin.Result it is a sealed class, so Swift and JavaScript callers can read the failure as data. See ADR-0004.

• GeoJSON: GeoPoint(45.5, -122.6, 100.0).toGeoJson() (RFC 7946).

Locale.displayName from the bundled resource data is always English. To show a locale's name in the end user's own language:

localeFor("bn")?.localizedDisplayName() // "bengali" for a French user, "ベンガル語" for a Japanese user

Rather than bundling a full translation matrix (~90 × 90 names) into every app, this delegates to the CLDR data each platform already ships — java.util.Locale (JVM/Android), NSLocale (Apple), Intl.DisplayNames (JS/Wasm). Bundled resource files aren't viable everywhere: browsers can't read files synchronously, and klibs can't deliver resources into an iOS app bundle.

Tradeoffs to be aware of:

• Names come from the OS, so wording may differ slightly between platforms and OS versions (e.g. "Chinese (Simplified)" vs "Simplified Chinese").
• Linux targets have no system CLDR data — they always return the English fallback.
• Browsers need Intl.DisplayNames (widely available since ~2020); older environments fall back to English.
• The function never returns null — the worst case is the English displayName.

See ADR-0003 for the full rationale, and issue #20 for the deferred bundled-tables alternative.

To ensure mathematical precision and behavior consistency, this library employs rigorous Differential Parity Testing against standard baseline libraries:

• JVM Baseline: Parity verified against standard JDK types (java.math.BigInteger and java.math.BigDecimal).
• KMP Baseline: Parity verified against the official Multiplatform Ionspin BigNum library.