var besselj/*:BesselF*/ = (function() {
  var W = 0.636619772; // 2 / Math.PI

  var b0_a1a = [57568490574.0, -13362590354.0, 651619640.7, -11214424.18, 77392.33017, -184.9052456].reverse();
  var b0_a2a = [57568490411.0, 1029532985.0, 9494680.718, 59272.64853, 267.8532712, 1.0].reverse();
  var b0_a1b = [1.0, -0.1098628627e-2, 0.2734510407e-4, -0.2073370639e-5, 0.2093887211e-6].reverse();
  var b0_a2b = [-0.1562499995e-1, 0.1430488765e-3, -0.6911147651e-5, 0.7621095161e-6, -0.934935152e-7].reverse();

  function bessel0(x/*:number*/)/*:number*/ {
    var a=0, a1=0, a2=0, y = x * x;
    if(x < 8) {
      a1 = _horner(b0_a1a, y);
      a2 = _horner(b0_a2a, y);
      a = a1 / a2;
    } else {
      var xx = x - 0.785398164;
      y = 64 / y;
      a1 = _horner(b0_a1b, y);
      a2 = _horner(b0_a2b, y);
      a = M.sqrt(W/x)*(M.cos(xx)*a1-M.sin(xx)*a2*8/x);
    }
    return a;
  }

  var b1_a1a = [72362614232.0, -7895059235.0, 242396853.1, -2972611.439, 15704.48260, -30.16036606].reverse();
  var b1_a2a = [144725228442.0, 2300535178.0, 18583304.74, 99447.43394, 376.9991397, 1.0].reverse();
  var b1_a1b = [1.0, 0.183105e-2, -0.3516396496e-4, 0.2457520174e-5, -0.240337019e-6].reverse();
  var b1_a2b = [0.04687499995, -0.2002690873e-3, 0.8449199096e-5, -0.88228987e-6, 0.105787412e-6].reverse();

  function bessel1(x/*:number*/)/*:number*/ {
    var a=0, a1=0, a2=0, y = x*x, xx = M.abs(x) - 2.356194491;
    if(Math.abs(x)< 8) {
      a1 = x*_horner(b1_a1a, y);
      a2 = _horner(b1_a2a, y);
      a = a1 / a2;
    } else {
      y = 64 / y;
      a1=_horner(b1_a1b, y);
      a2=_horner(b1_a2b, y);
      a=M.sqrt(W/M.abs(x))*(M.cos(xx)*a1-M.sin(xx)*a2*8/M.abs(x));
      if(x < 0) a = -a;
    }
    return a;
  }

  return function besselj(x/*:number*/, n/*:number*/)/*:number*/ {
    n = Math.round(n);
    if(!isFinite(x)) return isNaN(x) ? x : 0;
    if(n < 0) return ((n%2)?-1:1)*besselj(x, -n);
    if(x < 0) return ((n%2)?-1:1)*besselj(-x, n);
    if(n === 0) return bessel0(x);
    if(n === 1) return bessel1(x);
    if(x === 0) return 0;

    var ret=0.0;
    if(x > n) {
      ret = _bessel_iter(x, n, bessel0(x), bessel1(x),-1);
    } else {
      var m=2*M.floor((n+M.floor(M.sqrt(40*n)))/2);
      var jsum=false;
      var bjp=0.0, sum=0.0;
      var bj=1.0, bjm = 0.0;
      var tox = 2 / x;
      for (var j=m;j>0;j--) {
        bjm=j*tox*bj-bjp;
        bjp=bj;
        bj=bjm;
        if (M.abs(bj) > 1E10) {
          bj *= 1E-10;
          bjp *= 1E-10;
          ret *= 1E-10;
          sum *= 1E-10;
        }
        if (jsum) sum += bj;
        jsum=!jsum;
        if (j == n) ret=bjp;
      }
      sum=2.0*sum-bj;
      ret /= sum;
    }
    return ret;
  };
})();