docs: function dgeom(prob, logp) {
        logp = logp === true;
  
        if (prob <= 0 || prob > 1 || utils.hasNaN(prob)) {
           return function(x) { return NaN; };
        }
  
        return function(x) {
           if (utils.hasNaN(x)) { return NaN; }
           if (x < 0 || Math.round(x) !== x) {
              return logp ? -Infinity : 0;
           }
           return logp ? Math.log(prob) + dbinomLog(x, prob)(0)
                       : prob * Math.exp(dbinomLog(x, prob)(0));
        };
     }