How can I make abbreviations expand instantly?

Question

Is there a way to make emacs expand abbreviations as soon as I finish typing them, rather than having to use a key combination, tab, or space?

For example, I want "`a" to expand to "\alpha". It would be nice if it could expand as soon as I type the "a".

I have tried abbrev-mode, but I can't figure out how to do expansions without typing a space (or other expansion character) after the abbreviation. The EmacsWiki explains how to prevent the expansion character from appearing after typing it, but that's not what I want. I also tried yasnippet, but it requires a trigger key, as far as I can tell from the documentation.

My specific motivation is to reproduce Vim-LaTeX-Suite macros, similar to this more general question asked here before.

Answer 1

Following Dan's suggestion, I figured it out using input methods:

(quail-define-package
 "vim-LaTeX-suite" "" "v-LTX-s" t
 "Input method to reproduce vim-LaTeX-suite keybindings"
 nil t nil nil nil nil nil nil nil nil t)

(quail-define-rules
 ("`a" ["\\alpha"])
 ("`b" ["\\beta"])
)

In vim-latex-suite, typing `/ for example produces \frac{}{<++>}<++>, with the cursor inside the first set of braces. This behavior can be reproduced using the advice feature of quail-define-rules. For example:

(quail-define-package
 "vim-LaTeX-suite" "" "v-LTX-s" t
 "Input method to reproduce vim-LaTeX-suite keybindings"
  nil t nil nil nil nil nil nil nil nil t)

; Jump cursor back to the first instance of <++>, like in vim-latex-suite
(defun my/quail-vls-jumper (str)
  (interactive)
  (let
    ((len (length str))
     (jpos (cl-search "<++>" str))
     )
    (if jpos
      (progn
        (backward-char (- len jpos))
        (delete-forward-char 4)
        (evil-insert-state)
        )
    )
  )
)

(quail-define-rules
 ((advice . my/quail-vls-jumper))
 ("`a" ["\\alpha"])
 ("`b" ["\\beta"])
 ("`/" ["\\frac{<++>}{<++>}<++>"])
 ("^^" ["^{<++>}<++>"])
)

I only started emacs and lisp in the last couple weeks, so there may be various bugs and poor style. But, this solution seems to work for me.