| use super::{expm1, expo2}; |
| |
| // sinh(x) = (exp(x) - 1/exp(x))/2 |
| // = (exp(x)-1 + (exp(x)-1)/exp(x))/2 |
| // = x + x^3/6 + o(x^5) |
| // |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub fn sinh(x: f64) -> f64 { |
| // union {double f; uint64_t i;} u = {.f = x}; |
| // uint32_t w; |
| // double t, h, absx; |
| |
| let mut uf: f64 = x; |
| let mut ui: u64 = f64::to_bits(uf); |
| let w: u32; |
| let t: f64; |
| let mut h: f64; |
| let absx: f64; |
| |
| h = 0.5; |
| if ui >> 63 != 0 { |
| h = -h; |
| } |
| /* |x| */ |
| ui &= !1 / 2; |
| uf = f64::from_bits(ui); |
| absx = uf; |
| w = (ui >> 32) as u32; |
| |
| /* |x| < log(DBL_MAX) */ |
| if w < 0x40862e42 { |
| t = expm1(absx); |
| if w < 0x3ff00000 { |
| if w < 0x3ff00000 - (26 << 20) { |
| /* note: inexact and underflow are raised by expm1 */ |
| /* note: this branch avoids spurious underflow */ |
| return x; |
| } |
| return h * (2.0 * t - t * t / (t + 1.0)); |
| } |
| /* note: |x|>log(0x1p26)+eps could be just h*exp(x) */ |
| return h * (t + t / (t + 1.0)); |
| } |
| |
| /* |x| > log(DBL_MAX) or nan */ |
| /* note: the result is stored to handle overflow */ |
| t = 2.0 * h * expo2(absx); |
| t |
| } |
