Flee Arrays and Collections

The Flee library supports loading values from arrays and collections on the expression owner.

• You simply need to use square brackets ([]) after the variable and specify an index which can itself be another expression or variable.
• If the variable being indexed is an array, Flee will emit IL optimized for loading array elements.
• If the indexed variable is not an array, Flee will try to find a default indexer property and use it instead.
• If the variable being indexed is not an array and does not have a default indexer, Flee will throw an ExpressionCompileException.

Let's consider the following class, which we will use as an owner class. It contains an array and collection.

class MyClass
{
    public int[] MyArray;
    public List<int> MyList;

    public MyClass()
    {
        MyArray = new int[] { 1, 3, 5, 7, 9};

        MyList = new List<int>() {0, 2, 4, 6, 8, 10};
    }
}

The following code shows how to index array and collection variables on the expression owner.

public static void Example1()
{
    MyClass owner = new MyClass();
    ExpressionContext context = new ExpressionContext(owner);
    context.Variables.Add("index", 2);

    string expression = "MyArray[3]";
    IGenericExpression<int> eGeneric = context.CompileGeneric<int>(expression);
    int result = eGeneric.Evaluate();
    Console.WriteLine("{0} = {1}", expression, result);

    expression = "MyList[index + 1]";
    eGeneric = context.CompileGeneric<int>(expression);
    result = eGeneric.Evaluate();
    Console.WriteLine("{0} = {1}", expression, result);
}

As you can see, we have defined an expression owner class with some array and collection members. Let's execute the above code, and you will see the following output.

MyArray[3] = 7
MyList[index + 1] = 6