Why is chop being ignored?

Question

If I use

Chop[10^-4, 10^-3]

then I'd expect the output to be zero. However, this is not the case. There is of course a very easy workaround since I can define my own "chop"

chop[x_,dx_] := If[Abs[x] < dx, 0, x]

but why is the innate version failing?

Please see this and the docs of Chop: "Chop works on both Real and Complex numbers." :) — Öskå, Jan 14 '15 at 15:40

score 8 · Accepted Answer · answered Jan 14 '15 at 15:41

The documentation states that Chop

replaces approximate real numbers in expr that are close to zero by the exact integer 0.

but you number is not approximate! Try

Chop[10^-4 // N, 10^-3]

It might be enlightening to evaluate 10^-4 // FullForm to see how 10^-4 is represented in Mathematica.

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