report.md

LSINF2335 - Programming Paradigms

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Project 2 report

Youri Mouton

Notes on using cop.rb

• It requires the sourcify gem.
• Strings in blocks provided in adapt should use single quotes, e.g, write
  {'ruby'}, not {"ruby"}.

Question 1

How do you save/restore the default implementation of a method.

The adaptations are structured in a hashmap of klass,methods where methods is a hashmap of method,impls and where impls is an array of the class CI. The class CI contains two variables, a Context' self value and the block itself.

On the first adapt call of a context, the existing methods of klass are added as first elements of the adaptations hashmap using instance_methods and binding the methods to the klass and thus get the default implementation.

The default implementation is restored by getting the first element of the adaptations array and defining the method to overwrite previous implementations resulting of activations.

Question 2

How do you ensure that the receiver is bound when an adaptation is installed?

Using define_method defines an instance method in the receiver. We have to use send to execute define_method on the klass because it is private.

The CI structure contains the receiver's self and the implementation to keep track.

Question 3

Can your framework adapt any method? Think about where methods can be defined and what parameters they can have. If no, why not? If yes, how did you do it?

My tests include defining adaptations with the following types of methods parameters, but all parameters types seem to be working:

type	test
required	{ |x,y| x + y }
optional	{ |x = 2| x }
array decomposition	{ |x,*y| y }
block	{ |&block| lambda { block } }

The framework can also adapt module methods easily as the following test shows:

module M
  def foo; 5; end
end

class T
  include M
end

class ModuleTests < Test::Unit::TestCase
  def test_module
    reset_cop_state
    c = Context.new
    c.activate
    c.adapt(M, :foo) { 1  }
    assert_equal(1, T.new.foo)
  end
end

Question 4

Describe the semantics of your extra feature. If any interesting tricks were used to implement it, mention them.

The extra feature I implemented is the following:

Make it so that multiple context activations require an equal number of context deactivation. Moreover, a context's adaptations priority should return to their previous priority.

The CI class was extended to add priority for an adaptation and the activate