from math import * # implementation adapted from cephes def polevl(x, coef): ans = coef[-1] for i in range(len(coef) - 2, -1, -1): ans = ans * x + coef[i] return ans sn = [ -2.99181919401019853726E3, 7.08840045257738576863E5, -6.29741486205862506537E7, 2.54890880573376359104E9, -4.42979518059697779103E10, 3.18016297876567817986E11 ] sn.reverse() sd = [ 1.00000000000000000000E0, 2.81376268889994315696E2, 4.55847810806532581675E4, 5.17343888770096400730E6, 4.19320245898111231129E8, 2.24411795645340920940E10, 6.07366389490084639049E11 ] sd.reverse() cn = [ -4.98843114573573548651E-8, 9.50428062829859605134E-6, -6.45191435683965050962E-4, 1.88843319396703850064E-2, -2.05525900955013891793E-1, 9.99999999999999998822E-1 ] cn.reverse() cd = [ 3.99982968972495980367E-12, 9.15439215774657478799E-10, 1.25001862479598821474E-7, 1.22262789024179030997E-5, 8.68029542941784300606E-4, 4.12142090722199792936E-2, 1.00000000000000000118E0 ] cd.reverse() fn = [ 4.21543555043677546506E-1, 1.43407919780758885261E-1, 1.15220955073585758835E-2, 3.45017939782574027900E-4, 4.63613749287867322088E-6, 3.05568983790257605827E-8, 1.02304514164907233465E-10, 1.72010743268161828879E-13, 1.34283276233062758925E-16, 3.76329711269987889006E-20 ] fn.reverse() fd = [ 1.00000000000000000000E0, 7.51586398353378947175E-1, 1.16888925859191382142E-1, 6.44051526508858611005E-3, 1.55934409164153020873E-4, 1.84627567348930545870E-6, 1.12699224763999035261E-8, 3.60140029589371370404E-11, 5.88754533621578410010E-14, 4.52001434074129701496E-17, 1.25443237090011264384E-20 ] fd.reverse() gn = [ 5.04442073643383265887E-1, 1.97102833525523411709E-1, 1.87648584092575249293E-2, 6.84079380915393090172E-4, 1.15138826111884280931E-5, 9.82852443688422223854E-8, 4.45344415861750144738E-10, 1.08268041139020870318E-12, 1.37555460633261799868E-15, 8.36354435630677421531E-19, 1.86958710162783235106E-22 ] gn.reverse() gd = [ 1.00000000000000000000E0, 1.47495759925128324529E0, 3.37748989120019970451E-1, 2.53603741420338795122E-2, 8.14679107184306179049E-4, 1.27545075667729118702E-5, 1.04314589657571990585E-7, 4.60680728146520428211E-10, 1.10273215066240270757E-12, 1.38796531259578871258E-15, 8.39158816283118707363E-19, 1.86958710162783236342E-22 ] gd.reverse() def fresnel(xxa): x = abs(xxa) x2 = x * x if x2 < 2.5625: t = x2 * x2 ss = x * x2 * polevl(t, sn) / polevl(t, sd) cc = x * polevl(t, cn) / polevl(t, cd) elif x > 36974.0: ss = 0.5 cc = 0.5 else: t = pi * x2 u = 1.0 / (t * t) t = 1.0 / t f = 1.0 - u * polevl(u, fn) / polevl(u, fd) g = t * polevl(u, gn) / polevl(u, gd) t = pi * .5 * x2 c = cos(t) s = sin(t) t = pi * x cc = 0.5 + (f * s - g * c) / t ss = 0.5 - (f * c + g * s) / t if xxa < 0: cc = -cc ss = -ss return ss, cc def eval_cornu(t): spio2 = sqrt(pi * .5) s, c = fresnel(t / spio2) s *= spio2 c *= spio2 return s, c