[IronPython] GetBoundMember for functions and properties

[Christian Schmidt]

Hi,

I'm embedding IP2 in an C# application. The user can extend objects by 
entering expressions based on the object's properties and expressions 
defined so far. That means an expression is evaluated in the object's 
"scope".
Now I want to allow expressions that reuse other expressions, but 
override the scope in which these referenced expressions are evaluated. 
For that the user should use the name of an expression and give the 
properties to override as keyword arguments.

Example:
class Transport {
   public double Distance { get; set; }
   public double Weight { get; set; }
   // ...
}
Expression "Freight" is defined by the user as:
 >>> Transport.Freight = "Distance * 1.1 * Math.Sqrt(Weight / 24000)"

 >>> t = Transport(Distance=100, Weight=6000)
 >>> print t.Freight
55

 >>> Transport.FreightFTL = "0.8 * Freight(Weight=24000)"
 >>> print t.FreightFTL
88

So when the expression Freight is evaluated the Weight property is 
overriden with 24000 and Distance is used normally from the object's scope.

I see 3 possible directions to achieve this:

1. Using GetBoundMember/GetCustomMember and somehow identify, if
the requested property is expected to be a function or a regular return 
type.

2. Accessing expression-properties returns an object that has a Call 
SpecialMethod with ParamDictionary args and a "default property" that 
returns the expression's value.

3. Parsing the expression and determine if the expression uses other 
expression in a functional context or normally as a property.


Does anyone have an idea how to achieve this or improve the design?

Thanks
Christian