Code Red > .NET

Can LispFunction return an atom ?

(1/2) > >>

gile:
Hi,

I try to learn C#, creating some LISP extensions.
I read some post (here and there) about ResultBuffer to get the function arguments and to return the function result.
But this way the returned value is a list, i.e. (don't laught, I'm a complete beginner)


--- Code: ---using System;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.DatabaseServices;

namespace DivLisp
{
    public class DivLisp
    {
        [LispFunction("div")]
        public ResultBuffer div(ResultBuffer args)
        {
            Array inputArgs = args.AsArray();
            double arg1 = Convert.ToDouble(((TypedValue)(inputArgs.GetValue(0))).Value);
            double arg2 = Convert.ToDouble(((TypedValue)(inputArgs.GetValue(1))).Value);
            ResultBuffer result = new ResultBuffer(new TypedValue((int)LispDataType.Double, (arg1 / arg2)));
            return result;
        }
    }
}
--- End code ---

Commande: (div 10 3)
(3.33333)

Is there a way so that a LISP function which requieres arguments returns an atom (i.e. (div 10 3) returns 3.33333)

It's Alive!:
Hi gile,

The LispFunction can return any of these types.

From the docs..
int
double
TypedValue
ResultBuffer
string
Point2d
Point3d
bool
void
ObjectId
SelectionSet


Since in C#, any type can be cast as an Object, you can just return an Object I.e


--- Code: ---   [LispFunction("Lisp1")]
    public static Object Lisp1(ResultBuffer resBuf)
    {
      if (resBuf == null)
      {
        return false;
      }
      else
      {
        return true;
      }
    }

--- End code ---

gile:
Thank you very much Daniel, it was so simple !!!

This made me understand a little more how works C# and how many I have to learn...

It's Alive!:
My pleasure  :-)

It's Alive!:
So let’s break down how AutoCAD ObjectARX interprets atoms and lists. ObjectARX sees lisp types as a resbuf, essentially a container that has a type code and a value. I.e. (5000 . “Gile”)  where the type code describes the type of the value. In C#, the basic type for getting and returning values to lisp is called a TypedValue, it’s essentially the same as ObjectARX’s resbuf as it contains a type code and an Object.

So a real number would look like
(LispDataType.Double  .  3.33333)

And a String
(LispDataType.Text .  “Gile”) 

Keep in mind that C# knows nothing of parenthesis or the dot in the dotted pair.
When returning custom lists to lisp, you must explicitly construct them

I.e
(LispDataType.ListBegin . null)
(LispDataType.Double  .  3.33333)
(LispDataType.DottedPair . null)
(LispDataType.Text .  “Gile”) 
(LispDataType.ListEnd  , null)

Would return (3.3333 . “Gile”)  to lisp

A ResultBuffer in C# is a container for TypedValue types. Its unmanaged type is a resbuf or resbuf chain


an example


--- Code: ---   [LispFunction("Lisp1")]
    public static Object Lisp1(ResultBuffer resBuf)
    {
      //++-- A new buffer to return
      ResultBuffer buf = new ResultBuffer();

      //make a list
      buf.Add(new TypedValue((int)LispDataType.ListBegin));
      buf.Add(new TypedValue((int)LispDataType.Double , 3.3333));
      buf.Add(new TypedValue((int)LispDataType.DottedPair));
      buf.Add(new TypedValue((int)LispDataType.Text, "Gile"));
      buf.Add(new TypedValue((int)LispDataType.ListEnd));

      return buf;
    }

--- End code ---


Sorry, I haven’t had my coffee yet, so I’m probably not doing this well

Navigation

[0] Message Index

[#] Next page