Augment Ruby's currying to handle MRI 2.1 required keyword arguments
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Gem Version

Augments Ruby currying to handle MRI 2.1 required keyword arguments.

Proc like objects can be curried until all their required keywords have been received

Please note:

  • Monkey patching is optional.
  • Ruby 2.1+ is required.
  • Optional keyword arguments cannot be curried.


Add this line to your application's Gemfile:

gem 'keyword_curry'

And then execute:

$ bundle

Or install it yourself as:

$ gem install keyword_curry


Monkey patching is optional

This gem merely adds a couple of modules and it's up to you whether you would like all of your Procs monkey patched.

The monkey patch version

require "keyword_curry"


You may wish for this behaviour only on special Procs

require "keyword_curry"

class SpecialProc < Proc
  include KeywordCurry::KeywordArgumentCurrying

  # ...

Currying Examples

The function is not invoked until all the arguments have been received. Each time a curried function is returned that will accept the next arguments.

Three keyword arguments one at a time

func = lambda { |a:,b:,c:| [a,b,c].join(" and ") } a: "A" ).call( b: "B" ).call( c: "C" )

=> "A and B and C"

In any order

func = lambda { |a:,b:,c:| [a,b,c].join(" and ") } b: "B" ).call( a: "A" ).call( c: "C" )

=> "A and B and C"

With any grouping

func = lambda { |a:,b:,c:| [a,b,c].join(" and ") } c: "C", b: "B" ).call( a: "A" )

=> "A and B and C"

Plays nice with positional arguments too

func = lambda { |first, a:,b:,c:| [first, a,b,c].join(" and ") }"first").call( c: "C", b: "B" ).call( a: "A" )

=> "First and A and B and C"


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request