Katsuyou / 活用 (lit. "Conjugation")

An API for conjugating Japanese words

Installation

Stick this in your Gemfile and 吸う it:

gem "katsuyou"

Usage

`Katsuyou.conjugate(word, type:)`

This gem generates conjugations for ichidan ("る") and godan ("う") verbs, as well as the two notable exceptions in suru (する) and kuru (来る). Other verbs exist (like nidan verbs), but as they're (apparently, I'm no expert) archaisms, I didn't bother implementing them.

Katsuyou.conjugate("食べる", type: :ichidan_verb)
Katsuyou.conjugate("聞く", type: :godan_verb)
Katsuyou.conjugate("学ぶ", type: "v5b")

# Our special cases
Katsuyou.conjugate("する", type: :suru_verb)
Katsuyou.conjugate("勉強", type: :suru_verb)
Katsuyou.conjugate("来る", type: :kuru_verb)

(By the way, if you're not sure what type of verb a given word is, consult a primer on verb groups and a dictionary to be sure)

And you'll get back a Struct subclass containing a number of conjugated forms:

conjugations = Katsuyou.conjugate("見せる", type: :ichidan_verb)

#  #<struct Katsuyou::VerbConjugation
#   conjugation_type=
#    #<struct Katsuyou::ConjugationType
#     code="v1",
#     description="Ichidan verb",
#     category=:ichidan_verb,
#     supported=true>,
#   present="見せる",
#   present_polite="見せます",
#   present_negative="見せない",
#   present_negative_polite="見せません",
#   past="見せた",
#   past_polite="見せました",
#   past_negative="見せなかった",
#   past_negative_polite="見せませんでした",
#   conjunctive="見せて",
#   conjunctive_polite="見せまして",
#   conjunctive_negative="見せなくて",
#   conjunctive_negative_polite="見せませんで",
#   provisional="見せれば",
#   provisional_negative="見せなければ",
#   volitional="見せよう",
#   volitional_polite="見せましょう",
#   imperative="見せろ",
#   imperative_negative="見せるな",
#   potential="見せられる",
#   potential_polite="見せられます",
#   potential_negative="見せられない",
#   potential_negative_polite="見せられません",
#   passive="見せられる",
#   passive_polite="見せられます",
#   passive_negative="見せられない",
#   passive_negative_polite="見せられません",
#   causative="見せさせる",
#   causative_polite="見せさせます",
#   causative_negative="見せさせない",
#   causative_negative_polite="見せさせません",
#   causative_passive="見せさせられる",
#   causative_passive_polite="見せさせられます",
#   causative_passive_negative="見せさせられない",
#   causative_passive_negative_polite="見せさせられません">

`Katsuyou.conjugatable?(word, type:)`

If you're not sure whether a particular word & type is supported, you can ask first with conjugatable? (note that conjugate() will raise if a conjugation type is unsupported or unknown)

Katsuyou.conjugatable?("食べる", type: :ichidan_verb) # => true
Katsuyou.conjugatable?("買う", type: "v5u") # => true
Katsuyou.conjugatable?("食", type: :ichidan_verb) # => false, all ichidan verbs end in る
Katsuyou.conjugatable?("ぷす", type: "v9s") # => false, unknown type "v9s"

Conjugation types

The conjugate(text, type:) method requires you to supply a type value. There are two categories of values that the gem accepts.

General conjugation types

First, as illustarted at the outset, these general conjugation types are supported:

ichidan_verb (e.g. 食べる)
godan_verb (e.g. 買う)
kuru_verb (e.g. 来る)
suru_verb (namely, する but also nouns that can take する like 勉強)

If you provide one of the above conjugation types, the gem will attempt to translate it to a more specific conjugation form, which are identified by the same codes as listed under conjugate-able entries' parts of speech in JMDict/EDICT.

Specific conjugation codes

As a result of the preceding, if you're passing in values from a JMDict-based dictionary, it probably makes more sense to pass the specific code (e.g. Katsuyou.conjugate("請う", type: "v5u-s")) to ensure that you get the most accurate results.

You can find codes the gem knows about in Katsuyou::CONJUGATION_TYPES.

For example to see the supported conjugation types:

puts Katsuyou::CONJUGATION_TYPES.select(&:supported).map { |type| "#  • #{type.code}" }.join("\n")
#  • v1
#  • v1-s
#  • v5aru
#  • v5b
#  • v5g
#  • v5k
#  • v5k-s
#  • v5m
#  • v5n
#  • v5r
#  • v5r-i
#  • v5s
#  • v5t
#  • v5u
#  • v5u-s
#  • vk
#  • vs
#  • vs-s
#  • vs-i

And likewise, for the known-but-unsupported ones:

puts Katsuyou::CONJUGATION_TYPES.reject(&:supported).map { |type| "#  • #{type.code}" }.join("\n")
#  • adj-i
#  • adj-na
#  • adj-t
#  • adv-to
#  • aux
#  • aux-v
#  • aux-adj
#  • v2a-s
#  • v4h
#  • v4r
#  • v5uru
#  • vz
#  • vn
#  • vr
#  • vs-c