// CS 2510 Fall 2013
// Assignment 3

import tester.*;

// to represent a list of Strings
interface ILoS {
    // combine all Strings in this list into one
    String combine();
}

// to represent an empty list of Strings
class MtLoS implements ILoS {
    MtLoS(){}
    
    // combine all Strings in this list into one
    String combine() {
       return "";
    }  
}

// to represent a nonempty list of Strings
class ConsLoS implements ILoS {
    String first;
    ILoS rest;
    
    ConsLoS(String first, ILoS rest){
        this.first = first;
        this.rest = rest;  
    }
    
    /*
     TEMPLATE
     FIELDS:
     ... this.first ...         -- String
     ... this.rest ...          -- ILoS
     
     METHODS
     ... this.combine() ...     -- String
     
     METHODS FOR FIELDS
     ... this.first.concat(String) ...        -- String
     ... this.first.compareTo(String) ...     -- int
     ... this.rest.combine() ...              -- String
     
     */
    
    // combine all Strings in this list into one
    String combine(){
        return this.first.concat(this.rest.combine());
    }  
    
}

// to represent examples for lists of strings
class ExamplesStrings{
    
    ILoS mary = new ConsLoS("Mary ",
                    new ConsLoS("had ",
                        new ConsLoS("a ",
                            new ConsLoS("little ",
                                new ConsLoS("lamb.", new MtLoS())))));
    
    boolean testCombine(Tester t){
        return 
            t.checkExpect(this.mary.combine(), "Mary had a little lamb.");
    }
}