m4tt30rru / lola

Language Of Language Augmentation (fork for paper)

Lola

The Language Of Languge Augmentation was found by Iddo Zmiry under the supervision of Prof. Yossi Gil in the Technion. Lola is a tool for language extensions and can equip any language with new syntax and semantics. Lola's syntax is Macro based, and designed to run on a precompiled code, transforming it from the new syntax to the domain syntax. Compared to other preprocessor tools, Lola is much more powerful and even allows the programmer to run python code.

Hello, Lola!

Lola's basic blocks are Lexis. A Lexi defines a pattern of code and some actions to apply on it whenever matched. Typically, a Lexi action will be replacing the code with domain code, asserting that some conditions apply and even running some python code.

Example

Range based loops are fun, they kill boiler plate, but don't exist in Java... Why not add them with the following Lexi?

##Find
  for(##Identifier(id) = ##Literal(from)..##Literal(to))
    ##any(block)
##replace
  for(int ##(id) = ##(from); ##(id) <= ##(to); ++##(id))
    ##(block)
##example
  for(i = 1..100)
    print(i);
##resultsIn
  for(int i = 1; i < 100; ++i)
    print(i);

* In the specification Lola uses @ to denote keywords prefix, but this sign is configurable. When we apply Lola to Java we use ## to not collide with annotations.

As can be deduced from the self explaining exmaple, a pattern is specified to find places where the lexi is used, a replace section specifies domain code to replace the matched code with, an example and resultsIn sections specify an example of usage and the code that will replace the example after applying the Lexi.

Note that the example is not only for documentation but for self testing too, when writing a Lexi, Lola asserts that the example indeed results in the specified resultsIn section code.

Another point worth noting is that Lola uses an environment for identifiers aliasing, meaning, if we write ##Literal(from), the matching literal will be stored in some environment (Jython actually) and may be summoned by the name from. For example, the ## keyword specifies a python snippet to run, so ##(from) will produce the literal matched by from.

Syntax

Lola's syntax is described by Iddo's thesis

Implementation

This version of Lola was implemented by @orimarco using Java 1.8. A detailed explanation about our implementation can be found in the Implementation Wiki.

How do I import the project?

Just clone/download the repository and import the project using Maven. Should be easy!

How do I use Lola?

After importing the project, Lola can be run by compiling Lola.java and running it in this form: Lola <input file> <output file>.