///|
/// Computes the Airy function Ai(x)
pub fn airy_ai(x : Double) -> Double {
  let arr_an : Array[Double] = [
    3.46538101525629032477e-01, 1.20075952739645805542e+01, 7.62796053615234516538e+01,
    1.68089224934630576269e+02, 1.59756391350164413639e+02, 7.05360906840444183113e+01,
    1.40264691163389668864e+01, 9.99999999999999995305e-01,
  ]
  let arr_ad : Array[Double] = [
    5.67594532638770212846e-01, 1.47562562584847203173e+01, 8.45138970141474626562e+01,
    1.77318088145400459522e+02, 1.64234692871529701831e+02, 7.14778400825575695274e+01,
    1.40959135607834029598e+01, 1.00000000000000000470e+00,
  ]
  let arr_afn : Array[Double] = [
    -1.31696323418331795333e-01, -6.26456544431912369773e-01, -6.93158036036933542233e-01,
    -2.79779981545119124951e-01, -4.91900132609500318020e-02, -4.06265923594885404393e-03,
    -1.59276496239262096340e-04, -2.77649108155232920844e-06, -1.67787698489114633780e-08,
  ]
  let arr_afd : Array[Double] = [
    1.33560420706553243746e+01, 3.26825032795224613948e+01, 2.67367040941499554804e+01,
    9.18707402907259625840e+00, 1.47529146771666414581e+00, 1.15687173795188044134e-01,
    4.40291641615211203805e-03, 7.54720348287414296618e-05, 4.51850092970580378464e-07,
  ]
  let arr_agn : Array[Double] = [
    1.97339932091685679179e-02, 3.91103029615688277255e-01, 1.06579897599595591108e+00,
    9.39169229816650230044e-01, 3.51465656105547619242e-01, 6.33888919628925490927e-02,
    5.85804113048388458567e-03, 2.82851600836737019778e-04, 6.98793669997260967291e-06,
    8.11789239554389293311e-08, 3.41551784765923618484e-10,
  ]
  let arr_agd : Array[Double] = [
    9.30892908077441974853e+00, 1.98352928718312140417e+01, 1.55646628932864612953e+01,
    5.47686069422975497931e+00, 9.54293611618961883998e-01, 8.64580826352392193095e-02,
    4.12656523824222607191e-03, 1.01259085116509135510e-04, 1.17166733214413521882e-06,
    4.91834570062930015649e-09,
  ]
  let mut domain_flag = 0
  let mut ai = 0.0
  if isinf(x) {
    return @double.not_a_number
  }
  if x > 103.892 {
    return 0.0
  }
  let mut f = 0.0
  let mut g = 0.0
  let mut k = 0.0
  if x < -2.09 {
    let z = 1.0 / (-2.0 * x * (-x).sqrt() / 3.0)
    let mut afn = 0.0
    for i = 0; i <= 8; i = i + 1 {
      afn = afn * (z * z) + arr_afn[i]
    }
    let mut afd = 0.0
    for i = 0; i <= 8; i = i + 1 {
      afd = afd * (z * z) + arr_afd[i]
    }
    let mut agn = 0.0
    for i = 0; i <= 10; i = i + 1 {
      agn = agn * (z * z) + arr_agn[i]
    }
    let mut agd = 0.0
    for i = 0; i <= 9; i = i + 1 {
      agd = agd * (z * z) + arr_agd[i]
    }
    let t = -2.0 * x * (-x).sqrt() / 3.0 + 0.25 * DOUBLE_PI
    let p = sin(t) * (1.0 + z * z * afn / afd) - cos(t) * (z * agn / agd)
    return 5.64189583547756286948e-01 / sqrt(sqrt(-x)) * p
  }
  if x >= 2.09 {
    domain_flag = 5
    let zeta = 2.0 * x * x.sqrt() / 3.0
    let mut an = 0.0
    for i = 0; i <= 7; i = i + 1 {
      an = an * (1.0 / zeta) + arr_an[i]
    }
    let mut ad = 0.0
    for i = 0; i <= 7; i = i + 1 {
      ad = ad * (1.0 / zeta) + arr_ad[i]
    }
    ai = 5.64189583547756286948e-01 *
      (an / ad) /
      (2.0 * x.sqrt().sqrt() * exp(zeta))
    if x > 8.3203353 {
      return ai
    }
  }
  f = 1.0
  g = x
  k = 1.0
  let mut m = 1.0
  let mut n = x
  let mut t = 1.0
  let z = x * x * x
  while t > 1.11022302462515654042e-16 {
    m *= z
    k += 1.0
    m /= k
    n *= z
    k += 1.0
    n /= k
    m /= k
    f += m
    k += 1.0
    n /= k
    g += n
    t = (m / f).abs()
  }
  if (domain_flag & 1) == 0 {
    return 0.355028053887817239260 * f - 0.258819403792806798405 * g
  }
  ai
}