Branch 1.10

Lama

is a programming language developed by JetBrains Research for educational purposes as an exemplary language to introduce the domain of programming languages, compilers and tools. Its general characteristics are:

• procedural with first-class functions - functions can be passed as arguments, placed in data structures, returned and "constructed" at runtime via closure mechanism;
• with lexical static scoping;
• strict - all arguments of function application are evaluated before function body;
• imperative - variables can be re-assigned, function calls can have side effects;
• untyped - no static type checking is performed;
• with S-expressions and pattern-matching;
• with user-defined infix operators, including those defined in local scopes;
• with automatic memory management (garbage collection).

The name is an acronym for Lambda-Algol since the language has borrowed the syntactic shape of operators from Algol-68; Haskell and OCaml can be mentioned as other languages of inspiration.

The main purpose of is to present a repertoire of constructs with certain runtime behavior and relevant implementation techniques. The lack of a type system (a vital feature for a real-word language for software engineering) is an intensional decision which allows to show the unchained diversity of runtime behaviors, including those which a typical type system is called to prevent. On the other hand the language can be used in future as a raw substrate to apply various ways of software verification (including type systems) on.

The current implementation contains a native code compiler for x86-32, written in OCaml, a runtime library with garbage-collection support, written in C, and a small standard library, written in itself. The native code compiler uses gcc as a toolchain.

In addition, a source-level reference interpreter is implemented as well as a compiler to a small stack machine. The stack machine code can in turn be either interpreted on a stack machine interpreter, or used as an intermediate representation by the native code compiler.

Language Specification

The language specification can be found here.

Installation

Windows users should get Windows Subsystem for Linux a.k.a WSL (recommended) or cygwin. Ubuntu-based variant of WSL is recommended.

• System-wide prerequisites:

  • sudo apt install gcc-multilib (in Debian-based GNU/Linux)
  • opam (>= 2.0.4)
  • OCaml (>= 4.10.1). Optional because it can be easily installed through opam. Compiler variant with flambda switch is recommended

• Check that opam is installed (using commands which opam or opam --version)

• Install right switch for OCaml compiler

  opam switch create lama ocaml-variants.4.10.1+fp+flambda

  In above command:

  • opam switch create is a subcommand to create a new switch
  • ocaml-variants.4.10.1+fp+flambda is name of a standart template for the switch
  • lama is an alias for the switch being created; on success a directory $(HOME)/.opam/lama should be created

• Update PATH variable for the fresh switch. (You can add these commands to your ~/.bashrc for convenience but they should be added by opam)

  export OPAMSWITCH=lama
  eval $(opam env)
  

  Check that OCaml compiler is now available in PATH: running which ocamlc should give /home/user/.opam/lama/bin/ocamlc (or similar) and ocamlc -v should give

  The OCaml compiler, version 4.10.1
  Standard library directory: /home/user/.opam/lama/lib/ocaml
  

• Pin Lama package using opam and right URL (remember of "#" being a comment character in various shells)

  opam pin add Lama https://github.com/JetBrains-Research/Lama-devel.git\#1.10+ocaml4.10 -y

  The -y switch meands "reply always 'yes'".

• Check that lamac exectuable was installed: which lamac should give

  /home/user/.opam/lama/bin/lamac
  

Smoke-testing:

Install lama system-wide, clone the repository and run make -C tutorial