Re: `make' written in elisp

[Richard Stallman]

    Automatically determining variables specific to the site the package
    is being installed at configuration time is a means to cut down load
    times.  There are things where it is not efficient or feasible to
    carry out the respective tests each time the package is loaded.

I am surprised to hear that.  Many Emacs Lisp packages search for
files they need to use, and they generally do so either when first
loaded into a session, or each time they are executed.  We have never
tried to make any of them save the results between sessions, but it
seems to be fast enough.

Is AUCTeX doing something that is particularly slow?

    Besides writing values to init files the configuration process is used
    to check if external tools required for building or running the
    package are present and provide necessary features.  A special case
    might be preview-latex which has a TeX part besides the Elisp part.

Why is it necessary to do this?
It seems to me that it would be just fine
to look for these things when the user tries to use them.

to try to use the command when the user asks to do