Script.NET

Script.NET
Paradigm(s)	imperative, meta, scripting
Developer	Microsoft
Typing discipline	dynamic
Influenced by	JavaScript
Platform	.NET Framework
License	Free

Script.NET or S# is a metaprogramming language that provides scripting functionality in Microsoft .NET applications, allowing runtime execution of custom functionality, similar to VBA in Microsoft Office applications. The syntax of Script.NET is similar to JavaScript. It is designed to be simple and efficient scripting language allowing to customize .NET applications. The language has a true runtime interpreter, and it is executed without generating additional in-memory assemblies.

Script.NET is an open-source project.

1 Metaprogramming features
2 Generalized objects
- 2.1 Definition
3 Examples
4 See also
5 External links

Metaprogramming features

Script.NET has a special quotation operator <[ program ]> which returns AST of a given program. Additionally, the AST of the current program may be accessed with the prog object.

Here is an example:

//Create an AST for MessageBox.Show('Hello'); program
ast = <[ MessageBox.Show('Hello'); ]>;
//Add this AST at the end of the current program
prog.AppendAst(ast);

The <[ ... ]> operator and prog objects allow Script.NET to generate new scripts or modify existing scripts at runtime.

Generalized objects

Script.NET includes so-called "Mutantic Framework" which introduces a special kind of "meta" objects for controlling objects of any type. It is composed of a set of classes, on top of which is the "DataMutant" class. It implements several principles of mutant object:

Definition

A Mutant is a special object which could have all properties (fields, methods, etc.), and may be converted to any type (or assigned to object of any type). The semantics of such conversion (or assignment) are pragmatically conditional.

There is a special operator := called Mutantic or Generalized assignment. Its purpose is to assign values of DataMutant fields to corresponding fields of an object of any type.

Example. Creation and Usage of MObject:

 // Create Data Mutant Object
 mobj = [ Text -> 'Hello from Mutant' ];
 // Set Additional Fields
 mobj.Top = 0;
 mobj.Left = 0;
 // Set corresponding fields of Windows Form object
 // (Mutantic Assignment)
 form := mobj;

Examples

Hello world

 MessageBox.Show('Hello World!');

Bubble sort function

a=[17, 0, 5, 3,1, 2, 55];
for (i=0; i < a.Length; i=i+1)
 for (j=i+1; j <  a.Length; j=j+1)
   if (a[i] > a[j] )
   {
     temp = a[i]; 
     a[i] = a[j];
     a[j] = temp;
   }
 
s = 'Results:';
for (i=0; i < a.Length; i++)
  s = s + ',' + a[i];
 
MessageBox.Show(s);

RSS Reader

a = new XmlDocument();
a.Load('http://www.codeplex.com/scriptdotnet/Project/ProjectRss.aspx');
 
MessageBox.Show('CodePlex Script.NET RSS::');
foreach (n in a.SelectNodes('/rss/channel/item/title'))
  MessageBox.Show(n.InnerText);

Stack

Stack limited to 10 elements using Design by contract feature

function Push(item)
[
//Limit to 10 items
 pre(me.Count < 10 ); 
 post();
 invariant();
]
{
 //me is mutated object, 
 //stack in this case
 me.Push(item);
}
 
function Pop()
[//Check emptiness
 pre(me.Count > 0);
 post();
 invariant();
]
{
 return me.Pop();
}
 
stack = new Stack<|int|>();
 
//Create Mutant
//1. Set Functions, override stack.Push
mObject=[Push->Push,PopCheck->Pop];
//2. Capture object
mObject.Mutate(stack);
 
for (i=0; i<5; i++)
  mObject.Push(i);
 
Console.WriteLine((string)mObject.PopCheck());