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 The M2 programming language

Last available version: 1.5-20110205

M2 is a new language for everyday programming: a clean syntax, simple as a scripting language, severe as a strong typed language, efficient like C. Those who know Modula-2 (from whom the name), Oberon or Pascal will find in M2 many similarities. Basically, M2 is a cross compiler from the M2 language to C. Array and dynamic structures are allocated automatically and deallocated when no more needed. The run-time checking prevent array index overflow and null-pointer dereferencing, so improving the robustness of the program. All the programmer must take care of is the algorithm, all the rest is in charge of the language. Features:

• Modularity
  Complete programs are MODULEs. A library is split in two pieces: the DEFINITION MODULE declares the interface, while the IMPLEMENTATION MODULE is its implementation (i.e. the code). A collections of libraries range from string manipulation to advanced cryptography. The opaque type FORWARD provide a way for encapsulating private data inside the implementation modules.

• Declarations
  CONSTants, TYPEs, VARiables and FUNCTIONs can be declared in a clean, neat way.

• Basic types:
  BOOLEAN, INTEGER (32 bit, 2-complement), REAL (64 bit), STRING (dynamically allocated, arbitrary length, any code including 0).

• Data structures
  ARRAY and RECORD can be combined together to build complex data structures. No "pointers" nor "references" are needed. ARRAYs and RECORDs are dynamically allocated assigning elements and fields. ARRAYs are of arbitrary length, and they grows simply adding elements.

• Recursion and nesting of the functions
  FUNCTIONs can be nested and called recursively. A function can return any type of data, including ARRAYs and RECORDs.

• Runtime checking on:
  substring range; dereferencing of unallocated structured variables; dereferencing of unallocated ARRAY elements.

• Memory garbage collector
  Data no more referenciable are automatically deallocated and the memory released.

• Error handling
  The TRY...CATCH instruction provide an effective way for handling errors sistematically.

• Postfix functional notation
  The first actual argument of a function may be prefix to the function name using the special arrow operator "->", so that f(a,b,c) may be rewritten as a->f(b,c). So, file->Open("data.txt") and window->Open() does not require the name of the function to be qualified as io.Open() or win.Open().

M2 is still a young project, and it lacks on many areas. M2 is a procedural language, but its "postfix" functional notation open the way to the object oriented programming paradigm. Unicode isn't supported, but the iconv library lets to convert strings between any charset representation.

Currently tested on: Red Hat Linux 7.3; Slackware 10.0; MS Windows 98 + Cygwin 1.5.

Hello, world!

Suppose we have this source program in the file hello.mod:

MODULE hello
IMPORT m2
VAR name: STRING
BEGIN
    print("Please, enter your name: ")
    name = input()
    print("Hello " + name + ", your first program is working!\n")
END

then, to compile and execute the program we give this command (bolded characters are those you have to type-in):

$ m2 -r hello.mod
Please, enter your name: Umberto
Hello Umberto, your first program is working!

More about M2

• REFERENCE
  The definitive guide to M2.
• REPORT
  (still only in italian language).
• TUTORIAL
  (still only in italian language).
• LIBRARY
  Standard modules.
• TEST ON-LINE
  Try on-line your M2 program.
• EXAMPLES
  Examples gallery. Compile and execute them on-line.
• APPLICATIONS
  Some applications already developed with M2.
• DOWNLOAD
  Source of the compiler and libraries.

License

The M2 language and the M2 developing system are released under a BSD-style license (see the file LICENSE for details).
The M2 compiler generates C source compilable with the "gcc" compiler, released under the GNU GPL license.
Some of the C libraries used by gcc are part of the GNU operating system and are released under the GNU GPL license.
The conservative garbage collector "gc" and the developing system "Cygwin" are released with their own license, but basically they can be used freely.
Some of the libraries provided with the M2 developing system are interfaces to other software that can or can not be installed in your system: if you plan to use that software, please read the respective license.

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