I was reading this page : C++ Tip: How To Get Array Length. The writer presented a piece of code to know the size of static arrays. template<typename T, int size> int GetArrLength(T(&)[size]){return size;} // what does '(&)' mean ? . . . int arr[17]; int arrSize = GetArrLength(arr); // arrSize = 17 Could anyone please shed the light o...
class Device def initialize(device_id, data_resource) @id = device_id @data_resource = data_resource end def display_device mode = @data_resource.get_display_device_mode(@id) presets = @data_resource.get_display_device_presets(@id) summary = "display_device: #{mode} ($#{presets})" return "* #{summary}" if p...
Is Template Metaprogramming faster than the equivalent C code ? ( I'm talking about the runtime performance) :) ...
class Product < ActiveRecord::Base set_table_name 'produce' end module ActiveRecord class Base def self.set_table_name name define_attr_method :table_name, name end def self.define_attr_method(name, value) singleton_class.send :alias_method, "original_#{name}", name singleton_class.class_eval do define_method(name) do value en...
lambda is used in this example in both the compose and the hydrate methods. What does lambda do here? def compose *lambdas if lambdas.empty? lambda { nil } elsif lambdas.size == 1 lambdas.first else lambda do |n| lambdas.first.call(compose(*lambdas[1..-1]).call(n)) end end end def hydrate(modulus, printabl...
Edit: I've edited the sample to better resemble the problem I have, now the function depends on a regular parameter (and not only on template parameters) which means that the computations can't be made at compile time. I wrote some code with a hand written typelist and now we've started using boost and I'm trying to move it to the mp...
I understand that it is possible to decorate methods with before and after hooks in ruby, but is it possible to do it for each line of a given method? For example, I have an automation test and I want to verify that after each step there no error shown on the page. The error is shown as a red div and is not visible to Ruby as raise or a...
I would like to debug some templated code to understand it better. Unfortunately I'm new to template metaprogramming and it IS hard for me to get in. When I try to output the preprocessed source files I get 125 000 lines of code :/ So is there a way I can see the generated Code? (The library I'm using is SeqAn) ...
Hi folks ... i have a problem .. i don't understand Template Metaprogramming. The Problem is : i read a lot . But it does not make much sense to me :/ Fact nr.1 : Template Metaprogramming is faster template <int N> struct Factorial { enum { value = N * Factorial<N - 1>::value }; }; template <> struct Factorial<0> { enum...
In Ruby I can add instance variables to a class by opening it, and doing something like this : class Whatever def add_x @x = 20 end end and this would add me an instance variable by the name of x. How can I do the same thing in Groovy? ...
Is it possible to intercept all the methods called in a application? I'd like to do something with them, and then let them execute. I tried to override this behaviour in Object.metaClass.invokeMethod, but it doesn't seem to work. Is this doable? ...
Will I learn anything in Metaprogramming Ruby that is not covered in any of: Programming Ruby, The Ruby Cookbook, The Ruby Programming Language or The Ruby Way, all of which have at least a chapter's material covering metaprogramming in Ruby? It also has about a third of the book devoted to Rails, which I'm not particularly interested i...
For the sake of simplicity, let's say I have a Person class in Python. This class has fields for firstname, lastname, and dob. class Person: def __init__(self, firstname, lastname, dob): self.firstname = firstname; self.lastname = lastname; self.dob = dob; In some situations I want to sort lists of Persons by lastname f...
I'm trying create a class which adds functionality to a generic class, without directly interfacing with the wrapped class. A good example of this would be a smart pointer. Specifically, I'd like to create a wrapper which caches all the i/o for one (or any?) method invoked through the wrapper. Ideally, the cache wrapper have the follo...
I have no idea how to "metatize" this method, but I know it should be simple. The method looks like this def check_sent=(value) Date.parse(value) rescue @dates_bad = true self.write_attribute(:check_sent, value) end This is for an ActiveRecord subclass. I would like to have these methods for all fields that I specify....
Does anyone have any experience with the JetBrains Meta Programming System? Is MPS better than, say, developing a DSL in Ruby? ...
Hi there , I have ported a C program to a C++ Template Meta program .Now i want to compare the runtime . Since there is almost no runtime in the C++ program , how should i compare these 2 programs. Can i compare C runtime with C++ compile time ? or is it just not comparable ? ...
In simple there is any way to redirect a page for every ten seconds in PHP ...
I have a Flickr interface that I wrote a while ago and part of it bothers me and I'd like to make it nicer. The way it works is I use method missing to construct the url parameters for the flickr call from the methods called on the flickr object, eg. @flickr.groups.pools.getPhotos(:user_id => "12656878@N06", :group_id => "99404851@N00")...
I would like to write a method in ruby that takes a class with certain methods and modifies its behavior by adding methods or changing how existing methods work. I would like to do this in a way that doesn't modify the base class so basically I want a function that takes a class and returns a new modified class without harming the initia...