mirror/v
1
0
Fork 0
mirror of https://github.com/vlang/v.git synced 2023-08-10 21:13:21 +03:00
Code Issues Projects Releases Wiki Activity

math: implement pow in pure V (#12105)

Browse Source
This commit is contained in:
playX
2021-10-08 17:44:55 +03:00
committed by GitHub
parent 60add6cc28
commit a8ace2c41c
10 changed files with 222 additions and 69 deletions
Download Patch File Download Diff File Expand all files Collapse all files

80
vlib/math/exp.v
View File

@@ -96,21 +96,8 @@ pub fn exp2(x f64) f64 {
return expmulti(hi, lo, k)
}
pub fn ldexp(x f64, e int) f64 {
if x == 0.0 {
return x
} else {
mut y, ex := frexp(x)
mut e2 := f64(e + ex)
if e2 >= math.f64_max_exp {
y *= pow(2.0, e2 - math.f64_max_exp + 1.0)
e2 = math.f64_max_exp - 1.0
} else if e2 <= math.f64_min_exp {
y *= pow(2.0, e2 - math.f64_min_exp - 1.0)
e2 = math.f64_min_exp + 1.0
}
return y * pow(2.0, e2)
}
pub fn ldexp(frac f64, exp int) f64 {
return scalbn(frac, exp)
}
// frexp breaks f into a normalized fraction
@@ -123,49 +110,40 @@ pub fn ldexp(x f64, e int) f64 {
// frexp(±inf) = ±inf, 0
// frexp(nan) = nan, 0
// pub fn frexp(f f64) (f64, int) {
// mut y := f64_bits(x)
// ee := int((y >> 52) & 0x7ff)
// // special cases
// if f == 0.0 {
// return f, 0 // correctly return -0
// if ee == 0 {
// if x != 0.0 {
// x1p64 := f64_from_bits(0x43f0000000000000)
// z,e_ := frexp(x * x1p64)
// return z,e_ - 64
// }
// if is_inf(f, 0) || is_nan(f) {
// return f, 0
// return x,0
// } else if ee == 0x7ff {
// return x,0
// }
// f_norm, mut exp := normalize(f)
// mut x := f64_bits(f_norm)
// exp += int((x>>shift)&mask) - bias + 1
// x &= ~(mask << shift)
// x |= (-1 + bias) << shift
// return f64_from_bits(x), exp
// e_ := ee - 0x3fe
// y &= 0x800fffffffffffff
// y |= 0x3fe0000000000000
// return f64_from_bits(y),e_
pub fn frexp(x f64) (f64, int) {
if x == 0.0 {
return 0.0, 0
} else if !is_finite(x) {
mut y := f64_bits(x)
ee := int((y >> 52) & 0x7ff)
if ee == 0 {
if x != 0.0 {
x1p64 := f64_from_bits(u64(0x43f0000000000000))
z, e_ := frexp(x * x1p64)
return z, e_ - 64
}
return x, 0
} else if abs(x) >= 0.5 && abs(x) < 1 { // Handle the common case
} else if ee == 0x7ff {
return x, 0
} else {
ex := ceil(log(abs(x)) / ln2)
mut ei := int(ex) // Prevent underflow and overflow of 2**(-ei)
if ei < int(math.f64_min_exp) {
ei = int(math.f64_min_exp)
}
if ei > -int(math.f64_min_exp) {
ei = -int(math.f64_min_exp)
}
mut f := x * pow(2.0, -ei)
if !is_finite(f) { // This should not happen
return f, 0
}
for abs(f) >= 1.0 {
ei++
f /= 2.0
}
for abs(f) > 0 && abs(f) < 0.5 {
ei--
f *= 2.0
}
return f, ei
}
e_ := ee - 0x3fe
y &= u64(0x800fffffffffffff)
y |= u64(0x3fe0000000000000)
return f64_from_bits(y), e_
}
// special cases are: