work in progress

lambda.rb

module Church
  Z    = -> (s) { -> (z) { z } }
  SUCC = -> (x) { -> (s) { -> (z) { s[x[s][z]] } } }
  ADD  = -> (x) { -> (y) { -> (s) { -> (z) { y[s][x[s][z]] } } } }

  def value(x, succ: -> (n) { n + 1 }, unit: 0)
    x[succ][unit]
  end
end

include Church

p value(SUCC[Z])
# ==> 1

p value(ADD[SUCC[SUCC[Z]]][SUCC[SUCC[SUCC[Z]]]])
# ==> 5