39 lines
781 B
V
39 lines
781 B
V
module math
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// scalbn scales x by FLT_RADIX raised to the power of n, returning the same as:
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// scalbn(x,n) = x * FLT_RADIX ** n
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pub fn scalbn(x f64, n_ int) f64 {
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mut n := n_
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x1p1023 := f64_from_bits(u64(0x7fe0000000000000))
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x1p53 := f64_from_bits(u64(0x4340000000000000))
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x1p_1022 := f64_from_bits(u64(0x0010000000000000))
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mut y := x
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if n > 1023 {
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y *= x1p1023
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n -= 1023
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if n > 1023 {
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y *= x1p1023
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n -= 1023
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if n > 1023 {
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n = 1023
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}
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}
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} else if n < -1022 {
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/*
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make sure final n < -53 to avoid double
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rounding in the subnormal range
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*/
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y *= x1p_1022 * x1p53
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n += 1022 - 53
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if n < -1022 {
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y *= x1p_1022 * x1p53
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n += 1022 - 53
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if n < -1022 {
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n = -1022
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}
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}
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}
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return y * f64_from_bits(u64((0x3ff + n)) << 52)
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}
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