hello richard,
thanks for your interest in maxima.
> http://riso.sourceforge.net/maxima/read_write_data-0.1.tar.gz
sorry, that's an experimental version that is long since superseded.
i should have erased it long ago. sorry for the confusion.
the most recent version is in the 5.9.2 tarball, which i guess you
must have since you mention recompiling maxima.
it is named "numericalio" now, which is unfortunately a misnomer
since it reads symbols and strings as well as numbers.
perhaps it should be renamed to "atomicio" or something since
those things are all atoms.
anyway, i believe load (numericalio); should load the lisp code.
the lisp code should be located at maxima/share/contrib/numericalio/,
which also contains several example input files and test scripts.
please try again and let us know how it turns out.
best,
robert dodier