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Test ducking build
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Duckling is a Haskell library that parses text into structured data.

"the first Tuesday of October"
=> {"value":"2017-10-03T00:00:00.000-07:00","grain":"day"}


A Haskell environment is required. We recommend using

On macOS you'll need to install PCRE development headers.
The easiest way to do that is with Homebrew:

brew install pcre

If that doesn't help, try running brew doctor and fix
the issues it finds.


To compile and run the binary:

$ stack build
$ stack exec duckling-example-exe

The first time you run it, it will download all required packages.

This runs a basic HTTP server. Example request:

$ curl -XPOST --data 'text=tomorrow at eight'

See exe/ExampleMain.hs for an example on how to integrate Duckling in your

Supported dimensions

Duckling supports many languages, but most don't support all dimensions yet
(we need your help!).

Dimension Example input Example value output
AmountOfMoney "42€" {"value":42,"type":"value","unit":"EUR"}
Distance "6 miles" {"value":6,"type":"value","unit":"mile"}
Duration "3 mins" {"value":3,"minute":3,"unit":"minute","normalized":{"value":180,"unit":"second"}}
Email "" {"value":""}
Numeral "eighty eight" {"value":88,"type":"value"}
Ordinal "33rd" {"value":33,"type":"value"}
PhoneNumber "+1 (650) 123-4567" {"value":"(+1) 6501234567"}
Quantity "3 cups of sugar" {"value":3,"type":"value","product":"sugar","unit":"cup"}
Temperature "80F" {"value":80,"type":"value","unit":"fahrenheit"}
Time "today at 9am" {"values":[{"value":"2016-12-14T09:00:00.000-08:00","grain":"hour","type":"value"}],"value":"2016-12-14T09:00:00.000-08:00","grain":"hour","type":"value"}
Url "" {"value":"","domain":""}
Volume "4 gallons" {"value":4,"type":"value","unit":"gallon"}

Extending Duckling

To regenerate the classifiers and run the test suite:

$ stack build :duckling-regen-exe && stack exec duckling-regen-exe && stack test

It's important to regenerate the classifiers after updating the code and before
running the test suite.

To extend Duckling's support for a dimension in a given language, typically 2
files need to be updated:

  • Duckling/<dimension>/<language>/Rules.hs
  • Duckling/<dimension>/<language>/Corpus.hs

Rules have a name, a pattern and a production.
Patterns are used to perform character-level matching (regexes on input) and
concept-level matching (predicates on tokens).
Productions are arbitrary functions that take a list of tokens and return a new

The corpus (resp. negative corpus) is a list of examples that should (resp.
shouldn't) parse. The reference time for the corpus is Tuesday Feb 12, 2013 at

Duckling.Debug provides a few debugging tools:

$ stack repl --no-load
> :l Duckling.Debug
> debug EN "in two minutes" [This Time]
in|within|after <duration> (in two minutes)
-- regex (in)
-- <integer> <unit-of-duration> (two minutes)
-- -- integer (0..19) (two)
-- -- -- regex (two)
-- -- minute (grain) (minutes)
-- -- -- regex (minutes)
[Entity {dim = "time", body = "in two minutes", value = "{\"values\":[{\"value\":\"2013-02-12T04:32:00.000-02:00\",\"grain\":\"second\",\"type\":\"value\"}],\"value\":\"2013-02-12T04:32:00.000-02:00\",\"grain\":\"second\",\"type\":\"value\"}", start = 0, end = 14}]


Duckling is BSD-licensed. We also provide an additional patent grant.

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