change of y range after compose/diff and div has no effect

[schmitts]

discussed on weboot-users@cern.ch

sschmitt:

Why does the following not change the y range?

http://127.0.0.1:6543/browse/docs/data/test_file.root/means/hist1,hist2/!compose/div/!range/y/20/40

On the other hand,

http://127.0.0.1:6543/browse/docs/data/test_file.root/means/hist1,hist2/!compose/stack/!range/y/20/40

works.

pwaller:

So the code which actually does the composition happens after the !range.
!compose is just an abstract thing which works against the next
multitraverser to its left (or should), regardless of where it exists in
the URL.

!range just calls SetRangeUser() on the object(s).

I think !compose/div produces a new histogram, rather than using existing
ones as !compose/stack does. Therefore, the range isn't transferred from
the input histograms to the new plot. That would be my guess.

Not sure what the solution is.

You could introduce a ?range parameter which affects the output of the
composition, but then this seems more complicated.

[pwaller]

Another thing which occurred to me is to have some sort of terminator:

/path/to/*/!compose/stack/additional/stuff/!/!argument_for_compose

Above, I used !, which would indicate the end of the "multi-traversal" and the start of arguments to the composed object itself.