[REBOL] Re: Examining the layout object
From: gscottjones:mchsi at: 1-Jul-2002 5:59
From: "Carl Read"
> I've been trying to write a script to examine layouts, but I always
> get an error. Here's an example of the problem...
> REBOL 
> examine: func [face][
> print type? face
> if not object? face [exit]
> print type? face/pane
> either block? face/pane [
> foreach pane face/pane [examine pane]
> examine face/pane
> lo: layout [text-list]
> examine lo
> And this is the output I get from it...
> ** Script Error: Cannot use subtract on block! value
> ** Where: pane
> ** Near: iter/offset: iter/old-offset: id - 1
> I'm totally stumped! Any ideas for what's wrong?
These out-of-no-where-and-seemingly-totally-"off-topic" errors are
frequently the result of indirectly evaluating an expression out of the
context. That was a convoluted sentence, I know. In this case that nested
structures reaches a point where pane is neither a block nor an object. It
is a function, and print is trying to evaluate that function without the
Given that I don't know your ultimate goals with your project, here is one
work-around that may help to get you back on track.
examine: func [face][
print type? face
if not object? face [exit]
either not error? try [print type? face/pane] [
either block? face/pane [
foreach pane face/pane [examine pane]
][print "error - this pane element is probably a function call"]
lo: layout [text-list]
Hope this is of some help. Maybe a guru will be able to articulate this
point more clearly.