GNU bug report logs - #75994
"seq -w" is broken for large enough numbers

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From: Pádraig Brady <P <at> draigBrady.com>
To: Alexey Dobriyan <adobriyan <at> gmail.com>, 75994 <at> debbugs.gnu.org
Subject: bug#75994: "seq -w" is broken for large enough numbers
Date: Sat, 1 Feb 2025 20:01:18 +0000

On 01/02/2025 17:43, Alexey Dobriyan wrote:
> coreutils 9.3, 9.5
> 
> Steps to reproduce:
> 
> 	# 21 digits
> 	$ seq 111111111111111111111 1 111111111111111111113
> 	111111111111111111111
> 	111111111111111111112
> 	111111111111111111113

With no -w, seq doesn't use floating point
and instead operates on the ASCII values directly.

> 
> 	$ seq -w 111111111111111111111 1 111111111111111111113
> 	111111111111111111112	# what?
> 	111111111111111111112
> 	111111111111111111112
> 	111111111111111111112


With -w seq will use long doubles internally,
which usually have a 64 bit significand.
I.e. once you go above 2^64, you get approximations of integers.

Now we could adjust seq to use the "ASCII" increment method
in this case by handling leading zeros appropriately.
It would be good to know your use case here though,
as to know how common this issue might be.

cheers,
Pádraig

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