lambda-mode.el

(require 'cl-lib)

(define-minor-mode lambda-mode
  "A minor mode to help type lambda terms.  Turns abbreviations
of the form \\lx into λx, with x being any letter."
  nil " λ" (make-sparse-keymap)
  (abbrev-mode (if lambda-mode 1 -1))
  (setq save-abbrevs nil))

(define-abbrev-table 'lambda-mode-abbrev-table
  (cl-loop for c from ?a to ?z
	   collecting (list (string ?\\ ?l c) (string ?λ c)))
  "Abbreviation table for `lambda-mode'"
  :regexp "\\(\\\\l[a-z]\\)")

(setq abbrev-minor-mode-table-alist
      `(,@abbrev-minor-mode-table-alist
	(lambda-mode . ,lambda-mode-abbrev-table)))