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Re: Arithmetic Zero

X-seq: zsh-users 29717
From: Lawrence Velázquez <larryv@xxxxxxx>
To: sergio <sergio@xxxxxxxxxxxxx>
Cc: "Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxx>, zsh-users@xxxxxxx
Subject: Re: Arithmetic Zero
Date: Tue, 05 Mar 2024 00:02:42 -0500
Archived-at: <https://zsh.org/users/29717>
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In-reply-to: <CAH+w=7ajHGSDi8pR5qb8k404UJ8ZybgXgyPdQ5PzvPRxccOm9A@mail.gmail.com>
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References: <47117922-e17f-44d1-8a2f-2cb4a9c53606@outerface.net> <CAH+w=7ajHGSDi8pR5qb8k404UJ8ZybgXgyPdQ5PzvPRxccOm9A@mail.gmail.com>

On Mon, Mar 4, 2024, at 11:23 PM, Bart Schaefer wrote:
> On Mon, Mar 4, 2024 at 7:28 PM sergio <sergio@xxxxxxxxxxxxx> wrote:
>> 1. What is the reason for returning 1 when an arithmetic evaluation
>> succeeds but is zero?
>
> (( ... )) is intended to be useful in tests:
>   if (( status == 1 )); then ...

Put another way, you can think of ((...)) as "translating" C's
notion of true/false into the shell's.  C considers zero-valued
expressions to be false, so ((...)) "translates" them into an exit
status of 1, which the shell considers false/failing.  Similarly,
C considers non-zero-valued expressions to be true, so for those
((...)) returns 0, which the shell considers true/successful.

-- 
vq

References:
- Arithmetic Zero
  - From: sergio
- Re: Arithmetic Zero
  - From: Bart Schaefer

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