why can many layers share one stream number?

Hi
I just dumped a techfile from a library, and found that in the
streamLayers() term, several layers can have the same stream number,
streamLayers(
;( layer streamNumber dataType translate )
;( ----- ------------ -------- --------- )
( ("m0" "drawing") 30 0 t )
( m0 0 0 nil )
( ("i0" "drawing") 31 0 t )
( ("i0" "net") 0 0 nil )
( ("m1" "drawing") 1 0 t )
( ("m3" "drawing") 10 0 t )
( ("m3" "net") 0 0 nil )
( ("r3" "drawing") 11 0 t )
( ("m3x" "drawing") 10 0 t )
)
II am confused about the meaning of stream number. If one number can
repreasent many layers, is the number useful? May anyone explain this
briefly or give me some guide to find the answer?

what is more, as the example above, there are two layers named "m0", in
my opinion, the default layerpurpose is "drawing", so does it mean that
the layers ("m0" "drawing") and "m0" are the same layer?

Thanks!

jren

 

Sure. pipo will just merge ("m3" "drawing") and ("m3x" "drawing")
on strmout. Beware that if you use the techfile (as opposed to
an external layer table) for strmin, you will get *either* m3 or m3x,
not both, and I'm not sure it's guaranteed which one. What I've
observed is that it uses the first entry, but I do not know if the
order of the table is guaranteed after the techfile is loaded.

That looks like a bad idea to me. The author is apparently hoping
to get only ("m0" "drawing") out, but all other purposes supressed.
But that's what you would get *without* the extra nil entry. If it
were mine, I would remove the nil entry.

-Jay-

 

Hmmm, "concatenate" would be a better word instead of
merge. "Merge" implies that overlapping polygons would
be merged into single polygons, and that will *not* happen.

-Jay-

 

Jay

Thanks a lot for your explanation!

jren