Hello grauzone,
BCS wrote:
Hello Robert,
BCS wrote:
Correct me if I'm wrong but I thing that D's opApply is a form of
the Visitor pattern where the calling function's stack frame is the
visitor object.
This just occurred to me. Maybe I've been missing something re the
visitor pattern but I think this make for a nice, cool and easy way
to describe it. (Also I don't remember it being described that way)
Er.... no. There's no double-dispatch (at least automatically),
there's only one foreach body delegate. The visitor pattern as far
as I know it uses dynamic dispatch so the visitor object can handle
different objects in the class hierarchy differently. For example,
you couldn't use a foreach to enumerate through a syntax tree and
handle expressions and statements differently (well, you could, but
you'd have to do it manually).
OK I'll grant that it doesn't follow the normal pattern to the letter
but it can be viewed as a degenerate case where there is only one
visitable type.
Does that mean all function calls are a degenerate case of the visitor
pattern?
no only when you pass a "action" memeber that is called on "stuff".
