/// <summary>
/// Default implementation of <see cref="IAccessorVisitor.Visit"/> that supports evaluation of intrinsic
/// functions Number(), String(), Boolean().
/// By overriding this any binding to to external objects can be achieved (recall to call this base
/// method when overriding).
/// </summary>
/// <param name="frame">The current frame (gives access to the next frame if any).</param>
public virtual PExpr Visit(IAccessorFrame frame)
{
IAccessorMemberFrame head = frame as IAccessorMemberFrame;
// We can only handle member access at the root level:
if (head == null)
{
return(frame.SetError());
}
// Lookup from the longest path to the head in registered objects:
// more "precise" objects mask root ones.
var deepestMemberFrame = frame.NextAccessors(true)
.Select(f => f as IAccessorMemberFrame)
.TakeWhile(f => f != null)
.LastOrDefault();
// We obtain at least the head, hence the do...while.
do
{
RuntimeObj obj;
if (_objects.TryGetValue(deepestMemberFrame.Expr.MemberFullName, out obj))
{
return(deepestMemberFrame.SetResult(obj));
}
deepestMemberFrame = deepestMemberFrame.PrevMemberAccessor;
}while(deepestMemberFrame != null);
var s = frame.GetImplementationState(c =>
c.On("Number").OnCall((f, args) =>
{
if (args.Count == 0)
{
return(f.SetResult(DoubleObj.Zero));
}
return(f.SetResult(args[0] as DoubleObj ?? DoubleObj.Create(args[0].ToDouble())));
}
)
.On("String").OnCall((f, args) =>
{
if (args.Count == 0)
{
return(f.SetResult(StringObj.EmptyString));
}
return(f.SetResult(StringObj.Create(args[0].ToString())));
})
.On("Boolean").OnCall((f, args) =>
{
return(f.SetResult(args.Count == 1 && args[0].ToBoolean() ? BooleanObj.True : BooleanObj.False));
})
);
return(s != null?s.Visit() : frame.SetError());
}