mixins

What's the difference between @Delegate and @Mixin AST transformations in Groovy. Maybe my question has to do with OO and when apply different patterns, but I use both and I can achieve the same behavior. class Person { String name = "Clark" def walk() { "Walk" } } @Mixin(Person) class Superhero { def fly() { "Fly" } } def superman = new Superhero() assert superman.name == "Clark" assert superman.walk() == "Walk" assert superman.fly() == "Fly" class Person { String name = "Clark" def walk() { "Walk" } } class Superhero { @Delegate Person person def fly() { "Fly" } } def superman = new

Is there a reasonable way in Python to implement mixin behavior similar to that found in Ruby -- that is, without using inheritance? class Mixin(object): def b(self): print "b()" def c(self): print "c()" class Foo(object): # Somehow mix in the behavior of the Mixin class, # so that all of the methods below will run and # the issubclass() test will be False. def a(self): print "a()" f = Foo() f.a() f.b() f.c() print issubclass(Foo, Mixin) I had a vague idea to do this with a class decorator, but my attempts led to confusion. Most of my searches on the topic have led in the direction of using

I have the following code from Programming Ruby 1.9 (slightly adapted) I just want to ensure my thought process is accurate module Trace def self.included(culprit) #Inject existing methods with tracing code: culprit.instance_methods(false).each do |func| inject(culprit, func) end #Override the singletons method_added to ensure all future methods are injected. def culprit.method_added(meth) unless @trace_calls_internal @trace_calls_internal = true Trace.inject(self, meth) #This will call method_added itself, the condition prevents infinite recursion. @trace_calls_internal = false end end end

Someone recently told me that Scala's traits aren't "true" traits, and that they were really just mixins. Unfortunately, I didn't get the opportunity to ask him why. Does anyone have an idea what he meant? Edit: As a definition of "traits," I have been referring to Nathanael Schärli’s dissertation and concept paper introducing traits. One key feature that seems to be missing from most mixin and/or multiple inheritance implementations is the ability to rename methods when you import them to avoid collision/ambiguity. Can Scala do that? Steve McDowell One key different between mixins and traits

I came across this question on modeling inheritance in Haskell and it reminded me that I have a little more complicated version of the same problem. I'll adopt the example from there because it's easier than thinking up my own. Suppose your program contains a number of types: data Camera = Camera ... data Light = SpotLight ... | DirectionalLight ... data Object = Monster ... | Player ... | NPC ... Now you want to implement some basic physics, so you want them all to have a position and a velocity, say of some type Vec3 . One way to do this is to declare a Physical typeclass with pos and vel

Here's the scenario: I'd like to have a host class that can have a variable number of mixins (not too hard with variadic templates--see for example http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103.144 ). However, I'd also like the mixins to be parameterized by the host class, so that they can refer to its public types (using the CRTP idiom). The problem arises when trying to mix the two--the correct syntax is unclear to me. For example, the following code fails to compile with g++ 4.4.1: template <template<class> class... Mixins> class Host : public Mixins<Host<Mixins>>... { public:

I am using LESS CSS . I am currently using Mixins with variables. Something like this works okay : .border-radius (@radius) { border-radius: @radius; } #header { .border-radius(4px); } This is not : .bg-img(@img) { background-image:url(@img); } #logo { .bg-img("../images/logo.jpg"); } i have tried combinations of using ' & " in the background-image:url ('') & ("") but then it tries to get the image as images/@img instead of the image name. other wise it gives me an error of Cannot call method 'charAt' of undefined I think writing background-image:url() all the time is too tedious, is this