46 lines
846 B
V
46 lines
846 B
V
|
module math
|
||
|
|
|
||
|
|
const (
|
||
|
|
tanh_p = [
|
||
|
|
-9.64399179425052238628e-1,
|
||
|
|
-9.92877231001918586564e+1,
|
||
|
|
-1.61468768441708447952e+3,
|
||
|
|
]
|
||
|
|
tanh_q = [
|
||
|
|
1.12811678491632931402e+2,
|
||
|
|
2.23548839060100448583e+3,
|
||
|
|
4.84406305325125486048e+3,
|
||
|
|
]
|
||
|
|
)
|
||
|
|
|
||
|
|
// tanh returns the hyperbolic tangent of x.
|
||
|
|
//
|
||
|
|
// special cases are:
|
||
|
|
// tanh(±0) = ±0
|
||
|
|
// tanh(±inf) = ±1
|
||
|
|
// tanh(nan) = nan
|
||
|
|
pub fn tanh(x f64) f64 {
|
||
|
|
maxlog := 8.8029691931113054295988e+01 // log(2**127)
|
||
|
|
mut z := abs(x)
|
||
|
|
if z > 0.5 * maxlog {
|
||
|
|
if x < 0 {
|
||
|
|
return f64(-1)
|
||
|
|
}
|
||
|
|
return 1.0
|
||
|
|
} else if z >= 0.625 {
|
||
|
|
s := exp(2.0 * z)
|
||
|
|
z = 1.0 - 2.0 / (s + 1.0)
|
||
|
|
if x < 0 {
|
||
|
|
z = -z
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
if x == 0 {
|
||
|
|
return x
|
||
|
|
}
|
||
|
|
s := x * x
|
||
|
|
z = x + x * s * ((math.tanh_p[0] * s + math.tanh_p[1]) * s + math.tanh_p[2]) / (((s +
|
||
|
|
math.tanh_q[0]) * s + math.tanh_q[1]) * s + math.tanh_q[2])
|
||
|
|
}
|
||
|
|
return z
|
||
|
|
}
|