  /* compute the logm1 link 
   * Args: 
   *   p: a positive scalar
   * Returns: 
   *   a scalar in (-Inf, Inf)
   */ 
   real logm1(real y) { 
     return log(y - 1);
   }
  /* compute the inverse of the logm1 link 
   * Args: 
   *   y: a scalar in (-Inf, Inf)
   * Returns: 
   *   a positive scalar
   */ 
   real expp1(real y) { 
     return exp(y) + 1;
   }
