func (i *Iter) Seek(offset int64, whence int) (int64, error) {
	var abs int64
	switch whence {
	case 0:
		abs = offset
	case 1:
		abs = int64(i.p) + offset
	case 2:
		abs = int64(i.rb.nsrc) + offset
	default:
		return 0, fmt.Errorf("norm: invalid whence")
	}
	if abs < 0 {
		return 0, fmt.Errorf("norm: negative position")
	}
	if int(abs) >= i.rb.nsrc {
		i.setDone()
		return int64(i.p), nil
	}

	// +3     +2      +1        0        -1     -2       -3
	// the offset to Thursday
	abs := t.abs()
	d := Thursday - absWeekday(abs)
	// handle Sunday
	if d == 4 {
		d = -3
	}
	// find the Thursday of the calendar week
	abs += uint64(d) * secondsPerDay
	year, _, _, yday := absDate(abs, false)
	return year, yday/7 + 1
}

    public BigDecimal div(Amount<Q> other) {
        return normalised.divide(other.normalised, 6, RoundingMode.HALF_UP);
    }

    public Amount<Q> abs() {
        if (value.compareTo(BigDecimal.ZERO) >= 0) {
            return this;
        }
        return new Amount<>(value.abs(), units);
    }

package cmplx

// Polar returns the absolute value r and phase θ of x,
// such that x = r * e**θi.
// The phase is in the range [-Pi, Pi].
func Polar(x complex128) (r, θ float64) {
	return Abs(x), Phase(x)

func (i *Iter) Seek(offset int64, whence int) (int64, error) {
	var abs int64
	switch whence {
	case 0:
		abs = offset
	case 1:
		abs = int64(i.p) + offset
	case 2:
		abs = int64(i.rb.nsrc) + offset
	default:
		return 0, fmt.Errorf("norm: invalid whence")
	}
	if abs < 0 {
		return 0, fmt.Errorf("norm: negative position")
	}
	if int(abs) >= i.rb.nsrc {
		i.setDone()
		return int64(i.p), nil
	}

}

// Check that it's using integer registers
func abs(x, y float64) {
	// amd64:"BTRQ\t[$]63"
	// arm64:"FABSD\t"
	// s390x:"LPDFR\t",-"MOVD\t"     (no integer load/store)
	// ppc64x:"FABS\t"
	// riscv64:"FABSD\t"
	// wasm:"F64Abs"
	// arm/6:"ABSD\t"
	// mips64/hardfloat:"ABSD\t"
	// mips/hardfloat:"ABSD\t"
	sink64[0] = math.Abs(x)

	// amd64:"BTRQ\t[$]63","PXOR"    (TODO: this should be BTSQ)

		delta := div32 - last
		consume(idx, delta*x)
		last = div32
	}
	consume(n-1, (1-last)*x)
}

func f64RelDiff(a, b float64) float64 {
	den := math.Max(math.Abs(a), math.Abs(b))
	if den == 0 {
		return 0
	}
	return math.Abs(a-b) / den

}

func genString(stddev float64) string {
	n := int(math.Abs(rand.NormFloat64()*stddev + stddev/2))
	c := make([]rune, n)
	for i := range c {
		f := math.Abs(rand.NormFloat64()*64 + 32)
		if f > 0x10ffff {
			f = 0x10ffff
		}
		c[i] = rune(f)
	}
	return string(c)
}

func genArray(n int) []any {
	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
	if f > n {
		f = n
	}

# Check that standard library packages are cached.
go list -json math # refresh cache
env GODEBUG=gofsystrace=1,gofsystracelog=fsys.log
go list -json math
! grep math/abs.go fsys.log

		// check output in table
		xi := &Int{abs: x}
		yi := &Int{abs: y}
		mi := &Int{abs: m}
		p := new(Int).Mod(new(Int).Mul(xi, new(Int).Mul(yi, new(Int).ModInverse(new(Int).Lsh(one, uint(len(m))*_W), mi))), mi)
		if out.cmp(p.abs.norm()) != 0 {
			t.Errorf("#%d: out in table=0x%s, computed=0x%s", i, out.utoa(16), p.abs.norm().utoa(16))
		}

		// check k0 in table
		k := new(Int).Mod(&Int{abs: m}, _B)
		k = new(Int).Sub(_B, k)