Unexpected results from Position

Asked Oct 24 '18 at 11:56

Active Oct 24 '18 at 12:12

Viewed 45 times

I am obtaining a very unexpected result and I would really like to not get this result:

vector = {1, 1, 1, 1/2, 1/2, 1/4, 1/4, 1/96 (11 + Sqrt[97]), 1/6, 1/6,
    1/8, 1/8, 1/10, 1/12, 1/12, 1/20, 1/20, 1/36, 1/36, 1/36, 1/36, 1/36,
    1/40, 1/80, 1/80, 1/96 (11 - Sqrt[97]), 1/96, 1/144, 1/144, 1/576, 1/576};

Position[vector, 1/2]

(*  Out[1224]= {{4}, {5}, {8, 2, 2, 2}, {26, 2, 2, 2, 2}}  *)

I am expecting the result to be {{4}, {5}}, I am very unsure where these extra values are coming from!

edited Oct 24 '18 at 12:12

Michael E2

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asked Oct 24 '18 at 11:56

wilsnunn

4

Use Position[vector, 1/2, 1] and to learn why take a look at FullForm of both vector and 1/2. – Kuba Oct 24 '18 at 12:00
@Kuba amazing thank you! – wilsnunn Oct 24 '18 at 12:02
Please note the tag [tag:bugs] has a very specific usage on this site. – Michael E2 Oct 24 '18 at 12:14
@MichaelE2 Sorry was unaware. I will know for next time. – wilsnunn Oct 24 '18 at 12:20
That's ok. Too many arcane practices for everyone to keep up with. :) – Michael E2 Oct 24 '18 at 12:21
The extra 1/2s comes from the fact that Sqrt is equivalently a 1/2-th power. Use FullForm[vector] to show the internal form used actually by the kernels. – Αλέξανδρος Ζεγγ Oct 24 '18 at 14:03
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The displayed form may substantially differ from the internal form – Kuba Oct 24 '18 at 20:06

Unexpected results from Position

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