\
infix, some nicer notation for set operations here

This is only for one level precedence so use parathesis
when you use them and logical operaors can be chained, e.g.
  
   (if (A ∋ x < a ≤ 1) f1 f2)

and          ∧ 
or           ∨
intersection ∩
union        ∪ 
set-minus    –  (Tex minus)
set-plus     ++ (Tex oplus was ugly in my emacs)
Logical operators are

   ∈ ⊂ ⊃ ∋ < > ≤ ≥ ≠

Operators supported are,

I'm using emacs cvs, M-X set-input-method TeX and you will get emacs symbols but the
backslash prefix will give you some pain.
\

(set *infixes* [])
(set *chains*  [])
(set *infixes* [[∧] [∨] [∩] [∪] [–] [++]])
(set *chains* [[∈ ⊂ ⊃ ∋] [< > ≤ ≥ ≠]])

(define infix?
  Op []     -> []
  Op [L|LL] -> (if (element? Op L)
                   L
                   (infix? Op LL)))

(define process-infix
  P [X]        -> X
  P [A Op | L] -> [(tr-op Op) A (process-infix P L)] where (element? Op P)
  P Z          -> (error "Wrong infix expression"))

\This is currently wrong in image\
(define process-chain
  P [A Op B]     -> [[(tr-op Op) A B]] where (element? Op P)
  P [A Op B | L] -> [[(tr-op Op) A B] and |(process-chain P [B|L])] where (element? Op P)
  P Z            -> (error "Wrong infix chaining expression"))


(define infix
  [define | L] -> [define|L] 
  [A Op ]      -> [A Op]
  [A Op | L]   -> (let P (infix? Op (value *infixes*))
                    (if (= P NIL)
                        (let P (infix? Op (value *chains*))
                          (if (= P NIL)
                              [A Op | L]
                              (process-infix [and] (process-chain P [A Op | L]))))
                        (process-infix P [A Op | L])))
  X            -> X)


(define tr-op
  ∨  -> or
  ∧  -> and
  ∩  -> intersection
  ∪  -> union
  –  -> difference
  ++ -> setplus
  X  -> X)

(set Ω [])

(defmacro ¬
  [X] -> [not X])

(sugar in infix 2)


(define setplus
  X Y -> (let S (X ∩ Y)
           ((X  S) ∪ (Y – S))))

(define ≤
  X Y -> (not (X > Y)))
(define ≥
  X Y -> (not (X < Y)))
(define ⊂
  X Y -> (= (intersection X Y) X))
(define ⊃
  X Y -> (= (intersection Y X) Y))

(define ∈
  X Y -> (element? X Y))
(define ∋
  X Y -> (element? Y X))