AjTalk: my Smalltalk-like interpreter project updated

I committed new code to my Google code project AjTalk:

http://code.google.com/p/ajtalk/

The previous version was described in my post

AjTalk- a Smalltalk-like interpreter

It’s an interpreter written using C#. This post describes the work in progress in this solution:

There are interfaces and base classes to support objects and classes:

Every method is compiled to bytecodes. Block and Method are the classes that contains bytecodes programs:

Blocks are anonymous code block. A Method has name and belongs to a class.

The bytecodes are described in an enumeration:

using System;

namespace AjTalk
{
    public enum ByteCode : byte
    {
        Nop = 0,
        GetVariable = 1,
        SetVariable = 2,
        GetArgument = 3,
        SetArgument = 4,
        GetConstant = 5,
        GetLocal = 6,
        SetLocal = 7,
        GetClassVariable = 8,
        SetClassVariable = 9,
        GetGlobalVariable = 10,
        SetGlobalVariable = 11,
        GetBlock = 12,

        GetSelf = 20,
        GetClass = 21,
        GetSuperClass = 22,
        NewObject = 23,
        Pop = 24,
        ReturnSub = 25,
        ReturnPop = 26,

        Add = 40,
        Substract = 41,
        Multiply = 42,
        Divide = 43,

        Send = 50
    }
}

In this committed version, there is support to create and access .NET objects. You can write

@System.IO.FileInfo new: ‘aFile.txt’

to create a new .NET object (@ is used to mark a name with special chars like ‘.’).

In this version, I added support to load .st files. It’s not an standard .st file: I will use this files to define the initial class library. Now, there are used only in tests. An example:

nil subclass: #Figure instanceVariables: 'x y'
!Figure methods!
x
    ^x
!
y
    ^y
!
x: newX
    x := newX
!
y: newY
    y := newY
! !

Figure subclass: #Rectangle instanceVariables: 'width height'
!Rectangle methods!
width
    ^width
!
height
    ^height
!

 I bootstrapped the system with a global nil variable. In the loader tests, the nil variable is bound to understand messages like subclass: and ifFalse:.

I changed the unit test to use VS test support. All in green:

The code coverage is good, 84.29%:

I added support to blocks in method, but there is no parameter support, yet:

nil ifFalse: [GlobalName := 'foo']

Next steps

The proposed roadmap is:

- Add more .NET object support

- Write the initial class in base library

- Implements Class, Metaclass, Behaviour “a la” Smalltalk-80

- Load initial library in console application

- Invoke AjTalk from .NET application

- Implements indexed variables

- Extends the bytecode set

As usual, I had fun written this code!

Angel “Java” Lopez
http://www.ajlopez.com/
http://twitter.com/ajlopez