code: public boolean isActive(final org.apache.tools.ant.Project p) {
      if (this.value == null) {
        return false;
      }
      if (this.ifCond != null && p.getProperty(this.ifCond) == null) {
        return false;
      } else if (this.unlessCond != null && p.getProperty(this.unlessCond) != null) {
        return false;
      }
      return true;
    }
docs: Returns true if the define's if and unless conditions (if any) are
  satisfied.