infocom/compilers/inform6/manuals/old/dm_supplement.txt

Many of us have been complaining for a while now that the DM no longer
warns the incautious user against the pitfalls of the objectloop
command.  I finally decided to go ahead and post this; if it makes it
into the next version of the DM, so much the better.  Actually, much of
the text comes straight from the 5.5 DM, but was removed when objectloop
was given expanded functionality in 6.0  The problem still remains,
though, and this fixes the oversight.  In addition, I added a couple
definitions of routines I've found useful in my Inform coding, as well
as noting slight mistake I found.

-Lucian Smith

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The following should be added to section 3.4, right after where it says
"'objectloop (x provides wingspan) ...' executes the code ... for each
object x in the game which is defined with a wingspan property.":
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� Certain forms of objectloop cycle through the object tree instead of
| simply looping over all objects in the game.  This happens for the
| keywords 'in', 'near', and (theoretically), 'from'.  'in' means through
| all the children of the given object, 'near' means through all the
| children of the parent of the object (including the object itself), and
| 'from' means from the given object through its siblings.  However, in
| Inform 6.15, 'from' does not work.  Also, you may not use 'near' or
| 'from' as logical tests, as you can with 'in' (which really means
| something different in this context).
| 
| �WARNING
| When using these keywords with objectloop, then, be careful if you are
| altering the object tree at the same time.  For instance, 
| 
| 	objectloop (x in rucksack) remove x;
| 
| is likely to go horribly wrong - it's safer not to cut down a tree
| while actually climbing it.  The safe way is to keep lopping branches
| off:
| 
| 	while (child(x)~=0) remove child(x);

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The following definitions should be added (in alphabetical order) to
Appendix 7: "Library-defined objects and routines"
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IndirectlyContains(x,y)
Returns true if y is a child of x, or a child of a child of x, or a
child of a child of a...(you get the idea).

PrintOrRun(x, prop, flag)
If x.prop is a string, this command prints the string, adds a new line,
and returns '1' (if 'flag' is 1, the new line is not printed).  If
x.prop is a routine, this command acts as if 'x.prop()' was called, and
returns whatever that routine returns.

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Exercise 78 (from Section 27:  Tokens of Grammar) and its answer refer
you to Appendix 9 for the specification of NounDomain.  They should
actually refer you to Appendix 7.