How do you get bit_length() in PARI/GP

Question

I've looked on google and couldn't find the answer and thought i'd ask PARI/GP users here. My question is simply How do you get bit_length() in PARI/GP, that you can use at there interpreter here: https://pari.math.u-bordeaux.fr/gp.html

score 3 · Answer 1 · answered Sep 19 '21 at 03:49

3

Probably the fastest way (for positive integers) is

len(n)=exponent(n)+1

answered Sep 19 '21 at 03:49

Charles

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score 2 · Accepted Answer · answered Sep 13 '21 at 18:07

2

For integers, it is just bit_length(n) = #binary(n);. For example:

bit_length(n) = #binary(n);
bit_length(100)
> 7

answered Sep 13 '21 at 18:07

Piotr Semenov

1,761
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24

score 1 · Answer 3 · answered Sep 14 '21 at 14:25

1

Faster for large numbers than binary is just to use logint (requires n > 0).

1 + logint(n,2)

answered Sep 14 '21 at 14:25

Andrew

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How do you get bit_length() in PARI/GP

3 Answers3