code: private PExp getExistsPredicate(ASetCompSetExp exp, ILexNameToken finmap,
  			ILexNameToken findex)
  	{
  		AApplyExp apply = getApplyExp(getVarExp(finmap), getVarExp(findex));
  
  		return getEqualsExp(apply, exp.getFirst());
  	}
docs: m(idx) = f(a)