Question

I writing a DSL in IronPython. Overloading operators in C# and using
them in python works fine, until you get to the assignation (=) operator.

Using the implicit cast overload solves the problem on the C# side, but it does not work in python.

This is the minimum example that reproduces the error:

class FloatValue
{  
  public FloatValue(float value)     
   {
    this.value = value;
   }

  public static implicit operator FloatValue(float value)
   {
     return new FloatValue(value);
   }

  public float value;
 }

Then I execute:

    FloatValue value = 5.0f  // It works!!!

But in Python:

# value is already an instance of FloatValue, it comes from somewhere. It's considered 
# an immutable value, so there is no problem with generating a new instance.

value = 5.0  # Assigns the value, but does not work :(

I get the following exception:

Expected FloatValue, got float

How can I make it work?

Answer 1

Python does not support single-precision floating point values. The literal 5.0 is therefore (in case of IronPython) represented as a System.Double.

You can either change your DSL to use double-precision or just implicitly convert down to float by adding

public static implicit operator FloatValue(double value)
{
    return new FloatValue(Convert.ToSingle(value));
}