pure interface of class PremonExp

public abstract class PremonExp
  extends Printable
{
    public PremonCat cat;
    public PremonType type;
    public PremonCon free;
    public abstract Mor semantics();
    public Mor semanticsFrom(PremonCon Gamma);
    public PremonExp apply(PremonExp N)
      throws TypeError;
    public PremonExp();
}