Exercises.

1. Write an FP function to reverse a list.

2. Write an FP function unique L. Unique accepts an input list, possibly infinitely long. It returns a list having the same members as L but with duplicates removed. The order of first occurrence must be maintained.

   eg.  unique ( 1::2::1::4::3::2:: ... )
      = 1::2::4::3:: ...
   

3. A node in a binary tree can be represented as a triple: elt::left::right. Write a functional program to build a binary search tree from a list of elements.

4. Extend the functional language parser to permit [a, b, c, ..., x] as a shorthand for a::b::c::...::x::nil and to allow "string" as shorthand for a list of characters ['s','t','r','i','n','g'].

5. Add a where clause to the language.

   let [rec] <decs> in <Exp>  =  <Exp> where [rec] <decs>