/// <summary>
/// Default function
/// </summary>
/// <para>
/// Swaps the elements at index a and b in a list
/// </para>
/// <param name="list_expr"> the target <see cref="DynamicList"/> (as an <see cref="Expression"/>)</param>
/// <param name="a_expr"> index of the first element</param>
/// <param name="b_expr"> index of the second element</param>
/// <returns> <see cref="NullVar"/> (equivalent of null/void)</returns>
private static NullVar swapFunction(Expression list_expr, Expression a_expr, Expression b_expr)
{
// evaluate every expression
DynamicList list = list_expr.evaluate() as DynamicList;
Integer a = a_expr.evaluate() as Integer;
Integer b = b_expr.evaluate() as Integer;
// check indexes
list.validateIndex(a);
list.validateIndex(b);
// extract both values
Variable var_a = list.atIndex(a);
Variable var_b = list.atIndex(b);
// freeze the context
Context.freeze();
// change a
list.removeValue(a);
list.insertValue(var_b, a);
// change b
list.removeValue(b);
list.insertValue(var_a, b);
// unfreeze the context
Context.unfreeze();
// update manually (void)
if (list.isTraced())
{
list.tracer.update(new Event(
new Alteration("swap", list, list.getRawValue(), new dynamic[] { a.getRawValue(), b.getRawValue() })));
}
return(new NullVar());
}
/// <summary>
/// Default function
/// </summary>
/// <para>
/// Creates a copy of a <see cref="DynamicList"/>
/// </para>
/// <param name="list_expr"> the target <see cref="DynamicList"/></param>
/// <returns> A new <see cref="DynamicList"/>. It's values are the same as the target list</returns>
private static Variable copyListFunction(Expression list_expr)
{
// evaluate every expression
Variable var_ = list_expr.evaluate();
Debugging.assert(var_ is DynamicList); // TypeError
DynamicList list = var_ as DynamicList;
// copy list
var raw = new List <dynamic>(list.getRawValue());
return(Variable.fromRawValue(raw));
}