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Questions tagged [metaprogramming]

Metaprogramming is the capability to reprogram ones programming environment, as with macros or metaclasses.

Metaprogramming - the capability to reprogram ones programming environment - can save time and code by allowing one to create new abstractions, or new and more concise syntax for repetitive tasks.

Notable metaprogramming facilities include:

  • Common lisp macros
  • Scheme hygienic macros
  • Common lisp metaobject protocol
  • Python metaclass facility
  • Smalltalk's entirely transparent and reflective execution environment

For more info see http://en.wikipedia.org/wiki/Metaprogramming.

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Python dictionary from an object's fields

Do you know if there is a built-in function to build a dictionary from an arbitrary object? I'd like to do something like this: >>> class Foo: ... bar = 'hello' ... baz = 'world' ... >>> f = Foo() >>> props(f) { 'bar' : 'hello', 'baz' :…
Julio César
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Get the name of the currently executing method

$0 is the variable for the top level Ruby program, but is there one for the current method?
salt.racer
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What exactly is metaprogramming?

I was reading an article on TheServerSide on ployglot programming on the Java platform. Some comments in the article refer to metaprogramming as the ability to generate code (perhaps on the fly). Is metaprogramming the ability to generate code on…
Parag
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Calling a Method From a String With the Method's Name in Ruby

How can I do what they are talking about here, but in Ruby? How would you do the function on an object? and how would you do a global function (see jetxee's answer on the post mentioned)? EXAMPLE CODE: event_name = "load" def load() puts "load()…
BuddyJoe
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Is it possible to implement dynamic getters/setters in JavaScript?

I am aware of how to create getters and setters for properties whose names one already knows, by doing something like this: // A trivial example: function MyObject(val){ this.count = 0; this.value = val; } MyObject.prototype = { get…
daiscog
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C++ SFINAE examples?

I want to get into more template meta-programming. I know that SFINAE stands for "substitution failure is not an error." But can someone show me a good use for SFINAE?
rlbond
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How do you pass arguments to define_method?

I would like to pass an argument(s) to a method being defined using define_method, how would I do that?
Sixty4Bit
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Conveniently Declaring Compile-Time Strings in C++

Being able to create and manipulate strings during compile-time in C++ has several useful applications. Although it is possible to create compile-time strings in C++, the process is very cumbersome, as the string needs to be declared as a variadic…
void-pointer
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Can a line of Python code know its indentation nesting level?

From something like this: print(get_indentation_level()) print(get_indentation_level()) print(get_indentation_level()) I would like to get something like this: 1 2 3 Can the code read itself in this way? All I want is the output from…
Fab von Bellingshausen
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Is it possible to figure out the parameter type and return type of a lambda?

Given a lambda, is it possible to figure out it's parameter type and return type? If yes, how? Basically, I want lambda_traits which can be used in following ways: auto lambda = [](int i) { return long(i*10);…
Nawaz
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What does send() do in Ruby?

Can someone please tell me what the following snippet obj.send("#{method_name}") is and does?
Christian Bankester
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Objective-C class -> string like: [NSArray className] -> @"NSArray"

I am trying to get a string name of a class from the class object itself. // For instance [NSArray className]; // @"NSArray" I have found object_getClassName(id obj) but that requires an instance be passed to it, and in my case that is needless…
Alex Wayne
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How Pony (ORM) does its tricks?

Pony ORM does the nice trick of converting a generator expression into SQL. Example: >>> select(p for p in Person if p.name.startswith('Paul')) .order_by(Person.name)[:2] SELECT "p"."id", "p"."name", "p"."age" FROM "Person" "p" WHERE…
Paulo Scardine
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How to drive C#, C++ or Java compiler to compute 1+2+3+...+1000 at compile time?

In a recent interview, I was asked a really strange question. The interviewer asked me how can I compute 1+2+3+...+1000 just using compiler features. This means that I am not allowed to write a program and execute it, but I should just write a…
TonySalimi
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Best introduction to C++ template metaprogramming?

Static metaprogramming (aka "template metaprogramming") is a great C++ technique that allows the execution of programs at compile-time. A light bulb went off in my head as soon as I read this canonical metaprogramming example: #include…
jwfearn
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