This page provides access to our implementation files for a simple functional OO Java-like language, FOOP. The implementation uses DemeterF and is described with respect to traversals in our OOPSLA 2008 submission.

The FOOP example shown in the paper is factorial:

class F{
    F(){ }
    int fact(int i){
        return if (i < 2) then 1 
               else i * this.fact(i + -1);
    }
}

new F().fact(7) // ==> 5040
    

Another more complicated example is a mini functional expression "interpreter":

class B{
    boolean b;
    B(boolean a){ b = a; }
    boolean toBool(){ return b; }
    B and(B a){ return new B(b && a.toBool()); }
    B or(B a){
       return new B( if(b) then true 
                           else if(a.toBool()) then true
                                else false );
    }
    B not(){ return new B( if(b) then false else true ); }
}

class I{
    int i;
    I(int j){ i = j; }
    int toInt(){ return i; }
    I incr(){ return this.add(new I(1)); }
    I add(I j){ return new I(i+j.toInt()); }
    B less(I j){ return new B(i < j.toInt()); }
    B equal(I j){ 
        return new B( if(i < j.toInt()) then false
                      else if(j.toInt() < i) then false
                           else true );
    }
}

(((new I(5).add(new I(14))).add(new I(-6))).less(new I(15))).not()).toBool() // ==> false
    

The files listed below make up the entire type checker and interpreter for FOOP. DemeterJ is used (the program.* files) to generate data structures and a parser. The Java files are DemeterF based traversal classes that transform the parse tree and type check and evaluate FOOP programs.

Eval.java is the most important file; containing a series of evaluators for various features of the language. Because DemeterF traversals are dynamic, we tested the evaluators iteratively adding methods to the classes to support each feature.