Usually in the literature it's  -\pi < Arg z \leq \pi
while arg z = Arg z + 2 \pi N, where N \in \nat

(though sometimes several authors may use these interchangeably or it could vary)

A suggestion would be to follow the above literature convention in the Library definitions too
(if practical enough)

Best,
Angeliki



On 2021-06-25 21:28, Lawrence Paulson wrote:
I’ve just noticed that we define both arg and Arg, the latter in
Complex_Transcendental.

The definitions are different but arg z = Arg z holds unconditionally.
It looks like a historical accident, maybe arg was introduced in the
1990s and forgotten about.

Interestingly enough, arg is used far more despite there being almost
nothing proved about it. Some lemmas are proved in
Complex_Geometry/More_Complex.thy, and many occurrences of “arg” are
simply variables.

This is a mess. Any suggestions? Maybe Arg could (temporarily) be made
an abbreviation for arg. Arg is the usual of the function (principal
value of the argument).

Larry

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