64 lines
2.2 KiB
V
64 lines
2.2 KiB
V
// Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module math
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const (
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uvnan = u64(0x7FF8000000000001)
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uvinf = u64(0x7FF0000000000000)
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uvneginf = u64(0xFFF0000000000000)
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uvone = u64(0x3FF0000000000000)
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mask = 0x7FF
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shift = 64 - 11 - 1
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bias = 1023
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normalize_smallest_mask = u64(u64(1) << 52)
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sign_mask = u64(0x8000000000000000) // (u64(1) << 63)
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frac_mask = u64((u64(1) << u64(shift)) - u64(1))
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)
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// inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
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pub fn inf(sign int) f64 {
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v := if sign >= 0 { math.uvinf } else { math.uvneginf }
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return f64_from_bits(v)
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}
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// nan returns an IEEE 754 ``not-a-number'' value.
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pub fn nan() f64 {
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return f64_from_bits(math.uvnan)
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}
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// is_nan reports whether f is an IEEE 754 ``not-a-number'' value.
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pub fn is_nan(f f64) bool {
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// IEEE 754 says that only NaNs satisfy f != f.
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// To avoid the floating-point hardware, could use:
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// x := f64_bits(f);
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// return u32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
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return f != f
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}
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// is_inf reports whether f is an infinity, according to sign.
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// If sign > 0, is_inf reports whether f is positive infinity.
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// If sign < 0, is_inf reports whether f is negative infinity.
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// If sign == 0, is_inf reports whether f is either infinity.
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pub fn is_inf(f f64, sign int) bool {
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// Test for infinity by comparing against maximum float.
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// To avoid the floating-point hardware, could use:
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// x := f64_bits(f);
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// return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
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return (sign >= 0 && f > max_f64) || (sign <= 0 && f < -max_f64)
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}
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pub fn is_finite(f f64) bool {
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return !is_nan(f) && !is_inf(f, 0)
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}
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// normalize returns a normal number y and exponent exp
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// satisfying x == y × 2**exp. It assumes x is finite and non-zero.
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pub fn normalize(x f64) (f64, int) {
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smallest_normal := 2.2250738585072014e-308 // 2**-1022
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if abs(x) < smallest_normal {
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return x * math.normalize_smallest_mask, -52
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}
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return x, 0
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}
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