Version 37 (modified by Jiri Svoboda, 13 years ago) ( diff )

Method overloading was rejected


An effort to design a high-level programming language for writing HelenOS severs and applications.

Note that Sysel syntax is not finalized. Some important language features are missing at the moment (especially visibility control and packaging) so the examples presented will need to change when these are implemented.


Sub-project name Status Description
Sysel Bootstrap Interpreter (SBI) In progress Interpreter of Sysel written in C. Runs in HelenOS and POSIX.
Sysel Compiler Toolkit (NNPS) Not started Modular compiler of Sysel written in Sysel itself. To produce C and/or LLVM IR.


SBI is an interpreter of Sysel currently in development. It is available stand-alone for POSIX or bundled with HelenOS (only in Bazaar repository, not yet in a stable release). You can run it with the command "sbi". Demos that you can run are available in /src/sysel/demos. Source files comprising the library are in /src/sysel/lib.

You can also run sbi without parameters to enter interactive mode.

Synopsis of current SBI features

  • Primitive types: bool, char, int, string
  • Compound types: class, multi-dimensional array
  • Other types: delegates, enumerations
  • Objective features: constructors, inheritance, grandfather class, static and non-static method invocation
  • Interfaces
  • Static functions, static member variables, static properties
  • Syntactic sugar: variadic functions, accessor methods (named and indexed properties), autoboxing
  • Arithmetic: big integers, addition, subtraction, multiplication, boolean operators
  • Static type checking (mostly), generic classes (unconstrained), exception handling
  • Bindings: Text file I/O, WriteLine, Exec

Missing SBI features

Should be addressed before phase 2:

  • Access control
  • Method overloading (rejected)
  • Code organization (packages and modules)
  • Explicit overriding (virtual, override)
  • Property overriding

Not necessary for phase 2:

  • Division
  • Structs
  • Working with binary data
  • Generic type constraints
  • Operator overloading

Janitorial tasks

  • Add cspan to all error and warning messages.
  • Most run-time errors should have been caught during static checking. They need to be reviewed, efectiveness of static checking verified and run-time errors converted to asserts.
  • All errors should be handled gracefully. Calls to exit() must be eliminated.


NNPS (Nativní Nástroje pro Překlad Syslu, en: Native Sysel Compilation Toolkit) is a prospective toolkit written in Sysel itself that should compile Sysel to binary form. Currently it is in preliminary experimentation/planning stage. Also current plan is to only implement a front end, transforming Sysel into low-level but machine-neutral IR. Most likely the first available output option should be C (used as if it were a machine-independent assembly) and the second LLVM IR. The native in NNPS means it is written in Sysel itself (i.e. it should be also self-hosting).

Ideally NNPS should compile natively in POSIX, cross-compile from POSIX to HelenOS and eventually compile natively in HelenOS. The eventually is there because an appropriate backend (i.e. a C compiler) needs to be ported to HelenOS before native compilation is feasible.

NNPS will be bootstrapped using SBI. That is by running SBI(NNPS(NNPS)) we will obtain a binary version of NNPS. This process will presumably require 'significant' computing resources since SBI is rather slow and consumes a lot of memory. Once compiled to binary form, NNPS should be much more modest.

Currently only the NNPS lexer has been implemented (as an experiment). When all missing SBI features listed as Should be addressed before phase 2 have been addressed, development focus should switch from SBI to NNPS.

Interesting reading material:

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