type of "location" argument

[Urs Liska]

Hi,

next helpless question: what Scheme type is the "location" argument used for Scheme functions?
(write)ing location gives

#<location /home/uliska/git/openLilyLib/snippets/editorial-tools/annotate/examples.ly:29:3>

While I didn't find anything about the "#<" combination in Scheme in general I have the impression that is an object of some kind.
Looking for the definition of ly:input-message I was lead to unsmob_input in input-smob.cc - but that doesn't help me any further to understand what's going on (I can read C++ like I can read a Spanish newspaper based on my knowledge of French and (partially) Italian).

How can I access the items in this location individually, at least the string, better the file, line and cursor position independently?
And how could I create something like ly:input-message, but without quoting the respective input?

I would like to create a clickable input message, but in the context of a series of information, so the output of the code context lines should be avoided.

Thanks
Urs