Proc#with – Partial Application

partial_application.rb

require 'forwardable'

class Proc
  def with(*arguments, &block)
    proc do |*remaining_arguments|
      call(*remaining_arguments, *arguments, &block)
    end
  end
end

class Method
  extend Forwardable
  def_delegator :to_proc, :with
end

class Symbol
  extend Forwardable
  def_delegator :to_proc, :with
end

Usage with Proc is a bit like "reverse currying"

f = ->(a, b, c) { (a + b) * c }

[1, 2, 3].map(&f.with(3, 2))
#=> [8, 10, 12]

The other methods are just convenience wrappers for Symbol

['foo', 'bar', 'baz'].map(&:center.with(10, '-'))
#=> ["---foo----", "---bar----", "---baz----"]

and Method objects

def piratize(string, seriousness: 3)
  "#{string} arr#{'r'*seriousness}!"
end

['foo', 'bar', 'baz'].map(&method(:piratize).with(seriousness: 4))
#=> ["foo arrrrrr!", "bar arrrrrr!", "baz arrrrrr!"]