Overview

This is a small experiment triggered by a Stackoverflow question which realizes a certain, flexible form of dynamic binding in Ruby.

In particular, using this we can run an existing Proc instance in a new context:

require 'dynamic_binding'

l = lambda { |a| a + foo }
foo = 2
l.call_with_binding(binding, 1)  # => 3

In addition to Proc#call_with_binding, we can also build up much more complex lookup scenarios:

require 'dynamic_binding'

l = lambda { |a| local + func(2) + some_method(1) + var + a }

local = 1
def func(x) x end

class Foo < Struct.new(:add)
  def some_method(x) x + add end
end

stack = DynamicBinding::LookupStack.new
stack.push_binding(binding)
stack.push_instance(Foo.new(2))
stack.push_hash(:var => 4)

p stack.run_proc(l, 5)  # => 15

Note that the lambda is defined at the beginning of the code, so none of the names it accesses are actually captured by its closure!