Lexesis

A language agnostic lexical analyser generator

Table Of Contents

• Introduction
• Requirements
• Building
• Getting started
• More examples
• Tested with
• Authors

Introduction

Lexesis is a language agnostic lexical analyser generator. Which means that it uses a description of tokens in the form of regular expressions, and outputs source files for a lexer/scanner (which can be in any language for which a backend has been built, currently only c++), which can be used in building a larger application. It's principle is very similar to the well known tools such as lex or flex, which the difference that Lexesis has a simpler input format, and does not depend on language specific actions to be specified in the configuration file. It uses a programming language independent description of the tokens, in order to allow a bigger reusability across different programming languages of the same lexical analyser specification.

This project came into existence as an application exercise in a course on regular languages and automata for the University of Antwerp.

Requirements

• git
• CMake 3.2.2+
• Boost variant header library (needed for mstch)

For those still on Ubuntu Trusty, the default cmake version is still 2.8.12, so there is a ppa available with a more up-to-date version.

Run

sudo apt-get update && sudo apt-get -y install software-properties-common; \
sudo add-apt-repository -y ppa:george-edison55/cmake-3.x; \
sudo apt-get update && sudo apt-get install -y cmake

to get this newer version

Used dependencies

The following dependencies will be automatically downloaded with git while building

• mstch
• optparse

Building

Get your terminal in the source tree and run the following commands:

mkdir build
cd build
cmake ..
make
make install

This will place the Lexesis executable in the build/bin folder, with some extra needed data for Lexesis in build/share You can now simply run ./bin/Lexesis with the arguments you like (see below and in the man pages for an overview).

Running tests

TODO

Getting started

Regular expressions

More examples

More examples can be found in the examples subdirectory, go ahead an have a look at them. Feel free to play around and experiment with them. The keywords example simply prints the lexed token type, along with its content, while the SyntaxHighlighter example is a bit more complete, making use of multiple lexers at once and providing a simple form of syntax highlighting for xml in the terminal using ansi escape codes. Be aware however that this also accepts anything that even remotely looks like xml, since the regular languages underlying the lexers cannot verify or parse xml. Additionally, the SyntaxHighlighter example also contains a couple of CMake rules that allow automatic generation and regeneration of lexer source files when the .lxs file changed. See the CMakeLists.txt if you are curious.

Tested with

OS	Compiler	Boost version
Ubuntu 14.04	gcc 5.3.0	Boost 1.54
Ubuntu 14.04	clang 3.5.0	Boost 1.54
Ubuntu 15.10	gcc 5.2.1	Boost 1.58
Ubuntu 15.10	clang 3.6.2-1	Boost 1.58
Arch linux	gcc 6.1.1	Boost 1.60
Arch linux	clang 3.8.0	Boost 1.60
OSX El capitan	clang 7.3.0	Boost 1.60

Authors

• Thomas Avé
• Robin Jadoul