You are currently viewing Code Writing Code: Metaprogramming Techniques to Implement in Languages and Frameworks

Code Writing Code: Metaprogramming Techniques to Implement in Languages and Frameworks

  • Post published:August 17, 2022

Technologies, opportunities, incredible tools, and frameworks have made web development a super flexible and instantaneous process. It is now possible to create any software or product that was previously considered to be impossible or magic.

Metaprogramming is one of those amazing programming techniques that have enabled programmers to work like wizards.

For example, among metaprogramming languages, Python metaprogramming has the most fame.

Are you wondering how? Let’s talk about it.

The Concept of Metaprogramming

“Code writing code – The Pragmatic Programmer (Andrew Hunt & David Thomas, p103)”

Metaprogramming is simply writing programs that write programs. An analogy that is often used is that of the car factory.

If you are a car builder, and you notice that some steps can be automated one day, what would you do? As a result, you automate this process and build a car factory. Then you realize that building your factory involves similar steps, so you automate them, creating a factory that makes factories that make cars. Metaprogramming is what this is.

If we understand it in terms of coding, then

In Python metaprogramming, every syntax is associated with a type. For instance, variable with integer value will have a type named ‘int.’ Hence, you can use the syntax ‘type()’ to include the type of anything.

How Does Metaprogramming Work?

It is a technique that treats code as data in computer programs. The concept is to write a program that writes another program and so on. Through it, computer programmers have greater flexibility because work usually done during the runtime period is moved to the compile time period. Since this process reduces the time it takes to manually write a program’s code, it frees up the programmer’s time for other tasks.

Using this example, you can understand it:

Assume you are a mechanic who builds automobile machinery. You realize that the systems can be automated for better performance during all these efforts. How would you react? You will automate all of your machinery items. Metaprogramming works similarly. The flow of one system creating another…

Metaprogramming Examples/Types

Interestingly, metaprogramming languages are used widely. There are a number of popular uses for it, including:

1- Domain Specific Languages (DSLs)

As the name implies, these (mini) languages are designed for specific applications. DSLs can be classified into two types:

External DSLs – Regardless of the language they are written in, external DSLs have their own identity. A good example of this is SQL, which integrates with the database.

Internal DSLs – They are similar to external DSLs, with the exception that they depend on the language they are written in. Furthermore, these languages extend existing languages rather than creating new ones.

2- Annotations

Understanding Java’s annotations is the best practice for metaprogramming. Annotations can be added to methods, fields, interfaces, classes, and packages in this language.

As a result of these annotations, the language is extended either at run-time or at compile-time.

3- Macros

Languages such as Rust, Scala, Lisp, and Clojure offer a mechanism called Macros for extending their capabilities.

If you want to know that macros in Rust can be spotted by ! (exclamation point). Macros, however, are similar to function calls. Nevertheless, they are operated slightly differently.

Metaprogramming: How do programs become data?

The following chart illustrates how metaprogramming is used in these languages:

python metaprogramming

Note: ASTs stand for Abstract Syntax Trees, and UpMLs for Up Metalevels.

The Benefits of Metaprogramming

In addition to the advantages attached to metaprogramming, there are some drawbacks as well that we will discuss later below:

  • Through metaprogramming, you can extend the capabilities of programming languages by adding new ones (or classes even). 
  • There is no need to store variables in memory since everything is enclosed in a string and executed correctly. Hence, performance is improved. The best way is implemented in Python metaprogramming.
  • The codes are used to write codes, which makes a programmer less likely to use them. Isn’t that amazing? Metaprogramming literally reduces manual labor.

FYI: The use of macros (in C or C++) promotes code reusability and reduces development time.

  • As soon as the compilation task is complete, we usually call off. Compiling code from high-level languages into machine languages and finding errors are some of the wonders of metaprogramming.

The Challenges of Metaprogramming

Theoretically or practically, metaprogramming presents some challenges. We will shed some light on them in this section:

  • Templates for C++ metaprogramming don’t appeal to me.
  • Scala must write down the implementation or functionality of MP.
  • There are a few typing issues in MetaOCaml.
  • Metaprograms are quite difficult to debug. It may be due to the use of inappropriate and immature tools. 
  • Strings of codes from unreliable sources can be difficult to execute. For example, strings are difficult to execute in Python metaprogramming languages. 
  • The use of strings can lead to more bugs and reduce readability.
  • It is undoubtedly a mistake to introduce metaprogramming to beginners. The MP development process is complex for novice developers. It is impossible for developers who don’t understand the constructs to understand the codes written by others.

A Variety of Metaprogramming Scenarios

Rather than talking a lot, we’ll present a lot more below. We have some code examples to help you understand the use of metaprogramming in various programming languages:

1) Metaprogramming in C++

Metaprogramming in C++

Brief logic: Using C++ metaprogramming templates, it was possible to incorporate compilers as interpreters.

The next important thing to learn is Python metaprogramming in which metaclasses are built.

2) Python Metaprogramming with Metaclasses

A simple problem of code repetition required debugging. Prior to executing its code body, we wanted to print out its fully qualified name to debug the class method.

To resolve the issue, we somehow did the following:

from functools import wraps
def debug(func):
”’decorator for debugging passed function”’
@wraps(func) def wrapper(*args, **kwargs): print("Full name of this method:", func.__qualname__) return func(*args, **kwargs) return wrapper
def debugmethods(cls):
”’class decorator make use of debug decorator
to debug class methods ”’
for key, val in vars(cls).items(): if callable(val): setattr(cls, key, debug(val)) return cls
class debugMeta(type):
”’meta class which feed created class object
to debugmethod to get debug functionality
enabled objects”’
def __new__(cls, clsname, bases, clsdict): obj = super().__new__(cls, clsname, bases, clsdict) obj = debugmethods(obj) return obj
base class with metaclass ‘debugMeta’
now all the subclass of this
will have debugging applied
class Base(metaclass=debugMeta):pass
inheriting Base
class Calc(Base):
def add(self, x, y):
return x+y
inheriting Calc
class Calc_adv(Calc):
def mul(self, x, y):
return x*y
Now Calc_adv object showing
debugging behaviour
mycal = Calc_adv()
print(mycal.mul(2, 3))

Output: 

Full name of this method: Calc_adv.mul

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In Summary:

This article examines how metaprogramming is implemented in different languages such as Python metaprogramming. We also discussed annotations, reflection, DSL, and macros. These tech enabled us to write code that contained less duplication and allowed greater flexibility in the written code.

It is indeed a good idea to use metaprogramming when writing code, and hopefully, this detailed discussion on metaprogramming will help you to understand and implement it effectively.