Aims

In this practical, you will build a basic library of ML functors that should be useful in the project.

Assessment

Your work will be assessed on the basis of the correctness and efficiency of the functors you implement. You will not be expected to provide implementations more efficient than those already covered in the notes and examples (but you will be expected to use the best implementations we have introduced so far).

Your code should be placed in the directory CS201/Prac5 under your home directory.

Deadline

The deadline for this practical is 6.00pm, Friday 22nd April.

1. You should implement functors (implementing the appropriate datatypes) with the following headers:

   functor QUEUE(type Item):QueueSig   functor STACK(type Item):QueueSig   functor PQUEUE(type Item val >: Item * Item -> bool):QueueSig     functor EQSET(type Item val ==:Item*Item -> bool):SetSig   functor ORDSET(type Item val >:Item*Item -> bool):SetSig     functor ASSOCLIST(type Item eqtype Key):DictSig

   The signatures referred to above are included in the prac5 ML database (the identifier == is also declared to be infix). The signatures SetSig and QueueSig are given in the notes; DictSig is given below.

   signature DictSig =  
   sig  
      type Key  
      type Item  
      type  Dict  
      exception Lookup  
      val empty  :  Dict  
      val lookup :  Dict -> Key -> Item  
      val remove : Key *  Dict ->  Dict  
      val enter  : (Key * Item) *  Dict -> Dict  
   end

   The signature DictSig refers to a dictionary—akin to the Environment used in the example covered in Lecture Note 11, but that does not include a remove operation—in which you can enter, and remove pairs consisting of a key and an associated item, and lookup the item associated with a given key. Your functor should use a list of pairs to implement the signature.

   The code for each functor should be placed in a file with the corresponding name, plus a .ML extension (for example, the code for the functor QUEUE should be placed in a file named QUEUE.ML).

2. You should also implement structures IntItem, StringItem, RealItem that can be passed as arguments to your functors, and use these to test your functors. Again, the code for each structure should be placed in a correspondingly named file with the .ML extension.