Re: can emacs do this

[Pascal J. Bourguignon]

Of course.  

Any question starting by "Can emacs do …" has a positive answer.  So
what's the purpose of asking?


> What facilities of emacs can be used for this?

Just use emacs, there's no need for anything special!

    (defun √ (x) (sqrt x))
    (√ 42) --> 6.48074069840786
    (defmacro λ (λ-list &rest body) `(lambda ,λ-list ,@body))λ
    (mapcar (λ (x) (* x x)) '(1 2 3 4)) --> (1 4 9 16)


There's also an alternative, where emacs displays eg. λ when there is
lambda in the file:

http://www.emacswiki.org/emacs/PrettySymbol
http://www.emacswiki.org/emacs/PrettyGreek

-- 
__Pascal Bourguignon__                 http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk