My name is Pascal Levy and I am an iOS and Mac OS X developer. I live 40 kilometers south west of Paris. I drink English tea and I ride a Japanese motorbike (the opposite would have been great too but far more expensive). Æquans is the name I am hiding behind since 2010 to release applications, libraries, and documents related to mobile development.

This nice name comes from a mathematical theory developed by Ptolemy in the 2nd century AD to account for planetary movements. No need to say this theory is nowadays completely outdated, but the word sounds good and it is related to astronomy, which is a personal interest and the topic of one of my applications.


I worked on a lot of projects, most of them in commercial companies. Beside those presented on this site, here are the most significant ones:

  • Balade à ciel ouvert, a planetarium application that used to be famous in the 90’s. The challenge was to perform intensive astronomical computations, graphics, and audio decompression on PC’s available at this time, which took a bit of cleverness and a lot of assembly language.
  • HB++, a language and a compiler that used to be one of the main development tool for Palm OS. If you owned a Palm device, probably some of the applications that were running on it were created with HB++.
  • Diabeo, a companion application to help in curing diabetes. It brings together an expert system embedded in a mobile application for the patient, and a telemedicine portal for the practitioner.

Professionally, I now work on software medical devices, especially a language and a compiler that allows specification, implementation and testing of medical algorithms. In my spare time, I work on a framework to do functional reactive programming in Swift, on a few iOS, Mac OS X and Ubuntu applications, and I am learning Haskell.


Expert in C/C++/Objective-C, and in x86, ARM and M68000 assembly languages. Intermediate level in Swift. Some casual developments in Java, Python and bash. Beginner in Haskell and OCaml.

Good knowledge of web technologies: HTML, CSS, PHP, JavaScript, XML, JSON, AJAX… Incidentally, this web site is entirely handcrafted. Some experiences in designing and implementing a REST API.

Significant experience in compiler design: lexical and syntactic analyzers, algorithms for type inference, abstract syntactic tree transformations, code or bytecode generation both for register and stack machines. Implementation of virtual machines.

Good experience in cryptography. Implementation of several algorithms (AES, RSA, hash functions, Diffie-Hellman, etc.) on mobile platforms when libraries that are now common were not available yet.

Interest in software localization. I designed a library and a toolset allowing a better separation between business logic code, which should be independent of the locale, and code that handles typographic and grammatical specificities of each language.

Good writing skills. Design and conduct of training courses on various topics, such as: software localization, floating point implementation, multithreading, cryptography, object oriented programming, functional programming.

And of course: design and implementation of a lot of iOS applications!