Introduction

Motivation

Why create yet another programming language? Like, there isn’t enough of them already?

I have asked myself these questions hundreds of times, over and over again. I can name dozens of possible arguments against creating a new programming language. I understand all the difficulties a language creator is doomed to face before he can gather any meaningful number of users of the new language. And I still believe that the creation of Jancy was justified. The truth is, Jancy was not created just to fix the infamous fatal flaw of other languages (aka they didn’t write it). Of course, the passion to invent was a significant driving force, but there was practical reasoning besides that.

During the development of a product called IO Ninja (a universal all-in-one low-level IO debugger) we were looking for a scripting language with the support for safe pointers and safe pointer arithmetics. We wanted to use scripting for adding new protocol analyzers and emulators, and the best way of parsing binary data is by a long shot C-structs and pointer arithmetics.

After not finding such language, we basically had a choice: either we settle for some existing scripting language without safe pointer arithmetics (say, embedded Python) or create a new scripting language – tailor-suited for the binary data stream processing. Create it both for ourselves, and for other developers who could be in need for such a scripting language. Needless to say, we had chosen the latter option – otherwise, you would not be reading this manual.

Of course, besides featuring safe pointers and safe pointer arithmetics, Jancy offers a long list of other useful but rarely found facilities. So let’s outline the distinguishing features of Jancy below. And for those of you wondering what’s in a name, Jancy is an acronym: [in-between] Java-and-C.

Design Principles

  • Object-oriented scripting language for IO and UI programming with C-family syntax
  • ABI (application-binary-interface) compatibility with C
  • Automatic memory management via accurate GC (garbage collection)
  • LLVM (Low Level Virtual Machine) as a back-end

Key Features

  • High level of ABI and source compatibility with C
  • Safe pointers and pointer arithmetic
  • Spreadsheet-like Reactive Programming
  • Efficient regex-based switches for writing incremental lexers/scanners
  • Dynamic structures with variable-length fields
  • Dual error handling model which allows both throw-catch semantics and error code checks – with the same function!

Other Notable Features

  • Properties (the most comprehensive implementation thereof)
  • Multicasts and events (including weak events, which do not require to unsubscribe)
  • Scheduled function pointers
  • Deterministic resource release
  • Multiple inheritance
  • Const-correctness
  • Thread local storage
  • Weak pointers (do not retain objects)
  • Partial application for functions and properties
  • Context-sensitive dual modifiers
  • Bitflag enums
  • Perl-style formatting
  • Hexadimal, binary, raw and multi-line literals