code: function gamma(x) {
        var expx;
  
        expx = Math.exp(lgamma(x));
  
        return x > 0 && x === Math.round(x) ? Math.round(expx) : expx;
     }
docs: Computes $$\Gamma(x) = \int_0^\infty u^{x-1} e^{-u} du$$
  
  Inspired by code in the Gnu Scientific Library
  
  Also see: *A Precision Approximation of the Gamma Function*, by
  Lanczos, 1964
  @memberof basicFunc