[Ironpython-users] IronPython, Daily Digest 4/18/2013

CodePlex no_reply at codeplex.com
Fri Apr 19 09:23:33 CEST 2013

Hi ironpython,

Here's your Daily Digest of new issues for project "IronPython".

In today's digest:ISSUES

1. [New issue] IronPython ignores overridden TryUnaryOperation of DynamicObject that overrides TryUnaryOperation



1. [New issue] IronPython ignores overridden TryUnaryOperation of DynamicObject that overrides TryUnaryOperation
User Rauhotz has proposed the issue:

"IronPython (2.7.3) seems to not check the TryUnaryOperation with ExpressionType.IsFalse and ExpressionType.IsTrue for performing short-circuit evaluation of the logical AND and OR operations.

Here's an example that uses a class that inherits from DynamicObject. In C#, it works perfectly, but produces a wrong result if used in an IronPython expression. Is that behavior expected or a bug? How can i get IronPython to behave the same way as C#?

The class:
public class Dyn : DynamicObject
    private readonly string text;

    public Dyn(string text)
        this.text = text;

    public override string ToString()
        return this.text;

    public override bool TryBinaryOperation(BinaryOperationBinder binder, object arg, out object result)
        result = new Dyn(this + " " + binder.Operation + " " + arg);
        return true;

    public override bool TryUnaryOperation(UnaryOperationBinder binder, out object result)
        switch (binder.Operation)
            case ExpressionType.IsFalse:
            case ExpressionType.IsTrue:
                result = false;
                return true;

        return base.TryUnaryOperation(binder, out result);

The usage:
dynamic a = new Dyn("a");
dynamic b = new Dyn("b");
dynamic c = new Dyn("c");

var correct = a && b || c;

var engine = Python.CreateEngine();
var scope = engine.CreateScope();
scope.SetVariable("a", a);
scope.SetVariable("b", b);
scope.SetVariable("c", c);
var incorrect = engine.Execute("a and b or c", scope);

Console.WriteLine("Correct: " + correct);
Console.WriteLine("Incorrect: " + incorrect);

Correct: a And b Or c
Incorrect: b

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