Crate duckling 

Duckling (Rust)

A Rust port of Facebook’s Duckling — a library for parsing natural language into structured data.

Given a string like "tomorrow at 3pm" or "42 degrees fahrenheit", Duckling extracts “dimensions” such as URLs and times.

Supported dimensions

Time, Numeral, Ordinal, Temperature, Distance, Volume, Quantity, AmountOfMoney, Duration, Email, PhoneNumber, Url, CreditCardNumber.

Usage

use duckling::{parse, Entity, Locale, Lang, Context, Options, DimensionKind, DimensionValue,
               MeasurementValue, TimeValue, TimePoint, Grain};
use chrono::{NaiveDate, TimeZone, Utc};

let locale = Locale::new(Lang::EN, None);
let context = Context {
    reference_time: Utc.with_ymd_and_hms(2013, 2, 12, 4, 30, 0).unwrap(),
    ..Context::default()
};
let options = Options::default();

// Time — "tomorrow at 3pm" parses as a naive (wall-clock) time
let results = parse("tomorrow at 3pm", &locale, &[DimensionKind::Time], &context, &options);
if let DimensionValue::Time(TimeValue::Single { value: TimePoint::Naive { value, grain }, .. }) = &results[0].value {
    assert_eq!(*value, NaiveDate::from_ymd_opt(2013, 2, 13).unwrap().and_hms_opt(15, 0, 0).unwrap());
    assert_eq!(*grain, Grain::Hour);
} else { panic!("expected Naive time point"); }

// Temperature
let results = parse("80 degrees fahrenheit", &locale, &[DimensionKind::Temperature], &context, &options);
assert_eq!(results, vec![Entity {
    body: "80 degrees fahrenheit".into(),
    start: 0, end: 21, latent: Some(false),
    value: DimensionValue::Temperature(MeasurementValue::Value {
        value: 80.0, unit: "fahrenheit".into(),
    }),
}]);

// Numerals
let results = parse("forty-two", &locale, &[DimensionKind::Numeral], &context, &options);
assert_eq!(results, vec![Entity {
    body: "forty-two".into(),
    start: 0, end: 9, latent: Some(false),
    value: DimensionValue::Numeral(42.0),
}]);

Time: instant vs naive

Time values distinguish between absolute instants and wall-clock/calendar times:

• Naive — "5 pm", "tomorrow", "March 15th" — wall-clock times with no timezone assumption
• Instant — "now", "in 2 hours", "5 pm EST" — pinned to a specific UTC moment

// Naive: no timezone baked in
TimeValue::Single { value: TimePoint::Naive { value: NaiveDateTime, grain }, values: Vec<TimePoint> }

// Instant: absolute UTC moment
TimeValue::Single { value: TimePoint::Instant { value: DateTime<Utc>, grain }, values: Vec<TimePoint> }

An explicit timezone (e.g. "3pm CET") promotes any naive time to an instant.

Acknowledgements

This is a Rust rewrite of facebook/duckling, originally written in Haskell.

Structs

Context

Context for resolving parsed tokens into structured values.

Entity

A parsed entity extracted from text, with its position, matched text, and resolved value.

IntervalEndpoints

A resolved time value — either a single point or an interval.

Locale

A locale combining a language and optional region.

MeasurementPoint

A single endpoint in a MeasurementValue::Interval.

Options

Options for controlling parsing behavior.

Enums

DimensionKind

The kind of dimension to extract from text.

DimensionValue

The resolved value of a parsed entity.

Grain

Time grain, ordered from smallest to largest (Second < Minute < … < Year). Ordering matches Haskell Duckling’s derived Ord.

Lang

Supported languages.

MeasurementValue

A measurement with a numeric value and unit. Used by Temperature, Distance, Volume, Quantity, and AmountOfMoney dimensions.

Region

Supported regions for locale-specific behavior.

TimePoint

A resolved time point — either an absolute UTC instant or a naive wall-clock time.

TimeValue

A resolved time value — either a single point or an interval. Includes a values array of up to 3 next occurrences, matching Haskell’s TimeValue SingleTimeValue [SingleTimeValue].

Functions

parse

Parse natural language text and return structured entities.

parse_en

Convenience function to parse text with default settings for English.