Re: query-replace-interactive not documented

[Richard Stallman <rms@gnu.org>]

    I'd rather say that since we already have special symbols
    \1 \2 \3 \#1 \#2 \#3, that the most natural choice would probably be
    just \# for the match number.  Then we'd have

    \\label{fn:\,\# } RET

I am not sure \# makes sense to use inside \,.  It would also be
hard to implement.

    And it would probably make sense to define \# as a string component
    on its own, too, so that we can just write
    \\label{fn:\#} RET
    if we want to.

That is clean and natural, so I think it is a good feature.  However,
people will sometimes want to use the value in more complex
computations, rather than just substituting it.