docs: function(a, b) {
           return {
              d: function(x, logp) { return dbeta(a, b, logp)(x); },
              p: function(q, lowerTail, logp) {
                 return pbeta(a, b, lowerTail, logp)(q);
              },
              q: function(p, lowerTail, logp) {
                 return qbeta(a, b, lowerTail, logp)(p);
              },
              r: function(n) { return rbeta(a, b)(n); }
           };
        }