Introduction


Then how about constructing functions?  

structures with constructors are often used, e.g.

 	append(x,y) = case x of 
 		nil 	    -> y
 		Cons[x1,xs] -> Cons[x1,append(xs,y)]

constructors do not have associativity

eg. Cons[x1,Cons[x2,x3]] != Cons[Cons[x1,x2],x3]