Quater-imaginary base

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The quater-imaginary numeral system was first proposed by Donald Knuth in 1955, in a submission to a high-school science talent search. It is a non-standard positional numeral system which uses the imaginary number 2i as base. By analogy with the quaternary numeral system, it is able to represent every complex number using only the digits 0, 1, 2, and 3, without a sign.

Contents

[edit] Powers of 2i

n (2i)n
−8 1/256
−7 1/128 i
−6 −1/64
−5 −1/32 i
−4 1/16
−3 1/8 i
−2 −1/4
−1 −1/2 i
0 1
1 2i
2 −4
3 −8i
4 16
5 32i
6 −64
7 −128i
8 256

[edit] Decimal to quater-imaginary

Base 10 Base 2i Base 10 Base 2i Base 10 Base 2i Base 10 Base 2i
1 1 −1 103 1i 10.2 −1i 0.2
2 2 −2 102 2i 10.0 −2i 1030.0
3 3 −3 101 3i 20.2 −3i 1030.2
4 10300 −4 100 4i 20.0 −4i 1020.0
5 10301 −5 203 5i 30.2 −5i 1020.2
6 10302 −6 202 6i 30.0 −6i 1010.0
7 10303 −7 201 7i 103000.2 −7i 1010.2
8 10200 −8 200 8i 103000.0 −8i 1000.0
9 10201 −9 303 9i 103010.2 −9i 1000.2
10 10202 −10 302 10i 103010.0 −10i 2030.0
11 10203 −11 301 11i 103020.2 −11i 2030.2
12 10100 −12 300 12i 103020.0 −12i 2020.0
13 10101 −13 1030003 13i 103030.2 −13i 2020.2
14 10102 −14 1030002 14i 103030.0 −14i 2010.0
15 10103 −15 1030001 15i 102000.2 −15i 2010.2
16 10000 −16 1030000 16i 102000.0 −16i 2000.0

[edit] Examples

5 = 16 + (3\cdot-4) + 1 = 10301_{2i}
i = 2i + 2\left(-\frac{1}{2}i\right) = 10.2_{2i}
7 \frac{3}{4} - 7 \frac{1}{2}i = 1(16) + 1(-8i) + 2(-4) + 1(2i) + 3\left(-\frac{1}{2}i\right) + 1\left(-\frac{1}{4}\right) = 11210.31_{2i}

[edit] References

  • D. Knuth. The Art of Computer Programming. Volume 2, 3rd Edition. Addison-Wesley. pp. 205, "Positional Number Systems"