An Introduction to Metaprogramming

This is an article written by Ariel Ortiz, our professor. Where he talks about metaprograms, which are programs that generates other programs or program parts. So, metaprogramming means writing metaprograms. The most common ones include compilers, interpreters, parser generators, assemblers and preprocessors. We use metaprograms to reduce a tedious programming task.

A quine is a special kind of source code generator. It is a program that generates a copy of its own source as its complete output.

Ruby is a dynamic language that allow us to modify different parts of the program easily during runtime without having to generate source code explicitly. Ruby´s core API and frameworks employ this facility to automate common programming tasks. To accomplish the previous statement we have code as the attr_initialize method that takes as input a variable number of attribute name. Each of this attribute name has the same position reserved for it in the dynamically created initialize methos parameter “args” in order to set its initial value.

We use zip and each methods to iterate at the same time over the attributes declared in list “attrs” and the argument list “args”. As a final step we delegate the attr_accessor method to create the read/write access methods for all the declared attributes.

Metaprogramming should sound difficult or complicated, but once you are familiar with the techniques, it becomes easier. With metaprogramming we can automate error-prone or repetitive programming tasks. We can use it to pre-generate data tables, generate boilerplate code automatically that you can abstract into a function, or even to test ingenuity on writing self-replicating code.