Customizing an existing input method -- loading and overwriting issues

[Florian v. Savigny]

I have just started setting the TeX input method as my default for
text modes, but would like to input a few characters which are not
covered, and also input some things differently. I have tried the
following, which I got from emacswiki.org/emacs/TeXInputMethod:

 (let ((quail-current-package (assoc "TeX" quail-package-alist)))
        (quail-define-rules ((append . t))
                            ;; non-breaking space:
                            ("~" ? )
                            ;; double quotes:
                            (",,"  ?„) ; German  opening
                            ("''"  ?“) ; German  closing -- English opening
                            ("``"  ?”) ; English closing
                            ("<<" ?\«) (">>"  ?\») ; (French or Swiss; not 
needed, but inuitive)))

which seems to /basically/ work. However, I have not found out when
and how exactly to invoke this code such that it only really (but
always) modifies the TeX input method. Use `eval-after-load', perhaps?
But after loading which file?

The full path to the quail.elc file? If I do that, I get the startup warning:

       Symbol's value as variable is void: quail-package-alist

This is odd, because that variable IS defined in quail.el(.gz), in about line 
111.

"quail.el.gz" or "quail"? In that case, I get the startup warning:

       error: Invalid Quail map `nil'

The same error if I try "latin-ltx", where the TeX input method is
defined.

I seem to be making some rookie mistake here. Can anybody help me out?



Second, while we are at it, the documentation of `quail-define-rules'
simply says that it

"Define[s] translation rules of the current Quail package."

and lower down, it specifies that (append . t) means that "the
following rules should be appended to the rules of the current Quail
package".

This is ambiguous, but sounds more as if when (append . t) is not
specified, or is (append . nil), this means that the whole rules get
overwritten (i.e. replaced by the few you specify). Or does it mean
that INDIVIDUAL rules overwrite rules with the same car?  (Could it
then perhaps also be used to undefine individual rules?)


(BTW, I am aware I could hack the whole package and create my own
variant, but I think it's a more desirable practice to just customize
the few things you want to work differently.)


And third, also a very pressing need: I understand that mule means
something like "MUltiLingual Environment (for Emacs)", and I have
found that leim means "Library of Emacs Input Methods".

But what does quail mean? It is surely also an acronym?



Many thanks for help on any of this!


Florian



-- 

Florian von Savigny
Melanchthonstr. 41
33615 Bielefeld