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Branden Robinson" To: Alejandro Colomar Cc: Alejandro Colomar , =?utf-8?B?0L3QsNCx?= , linux-man@vger.kernel.org Subject: Re: [PATCH 4/5] tm.3type: describe tm_zone, tm_gmtoff Message-ID: <20251029223053.hbsbdsizoeoudejs@illithid> References: <62c1b6748d2faa6263264b9fcaa064495357441b.1658195739.git.nabijaczleweli@nabijaczleweli.xyz> <90beebd3-2636-21d5-323b-766c8d81d6d3@gmail.com> <20251029090718.6xpq6zf6iawjta2j@illithid> Precedence: bulk X-Mailing-List: linux-man@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nwz6r5hfgdqb5n7o" Content-Disposition: inline In-Reply-To: --nwz6r5hfgdqb5n7o Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 4/5] tm.3type: describe tm_zone, tm_gmtoff MIME-Version: 1.0 Hi Alex, At 2025-10-29T11:21:27+0100, Alejandro Colomar wrote: > On Wed, Oct 29, 2025 at 04:07:18AM -0500, G. Branden Robinson wrote: > > At 2022-07-19T14:17:15+0200, Alejandro Colomar wrote: > > > Could you come up with a more mathematically precise term for > > > "reverse"? What is reverse? The additive inverse? Maybe use > > > "additive inverse"? I think "opposite" also has the meaning of > > > additive inverse in maths, and it's maybe a simpler term (although > > > additive inverse is more precise, IMHO). But reverse is > > > definitely confusing to me. > >=20 > > I think the idiomatic term is "inverse". >=20 > Inverse is too generic. Inverse functions do something else. The > specific terms are "opposite (of a) number" and "additive inverse", > AFAIK, and maybe also "inverse (of a) number". Yes, but `tm_gmtoff` and `timezone` are _scalars_, not functions. tzset(3): extern long timezone; tm(3type): struct tm { =2E.. /* Since POSIX.1=E2=80=902024: */ long tm_gmtoff; /* Seconds East of UTC */ =2E.. } Consequently, if they possess an inversional relationship at all, they must be either additive or multiplicative inverses of the other,[1] and the page now makes it clear which. tm(3type): tm_gmtoff is the difference, in seconds, of the timezone represented by this broken=E2=80=90down time and UTC (this is the addi= tive inverse of timezone(3)). I apologize for re-raising an old and as far as I can tell, satisfactorily settled issue. I was looking at messages in neomutt with a non-obvious filter in place (meaning one I'd applied, wandered away =66rom the computer, and forgot about), and since your message of 19 July was still in my inbox, I got confused and thought it was an item still solicting my input. Regards, Branden [1] If there's another kind of inverse that can apply over the integers, I don't know what it is. --nwz6r5hfgdqb5n7o Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEh3PWHWjjDgcrENwa0Z6cfXEmbc4FAmkClZYACgkQ0Z6cfXEm bc5nEQ//eQe68JXi2G9Us3X307bqw0Iflf7iJpHtMr4eu+zhb6NKmbeHM7doR4rp O69wa077vsx3hOG304Ot9Udg7g3AkrMOsiu1J86lMrDm17CSgDYTo/oGfhxS/gey JqnoVEil8ZDSXAaRzdvYFk1wL1eONTpSjhV6gyjcpkUPMDgkqv7d190hxDM8/khm HjIbL3cq0Hk5bNRST1/HFG7G9WOYTbAGJX3qMtmKPLUG3SVnNV9/m+UTmSMKztj9 w+iLK1DMsE6gvPQi2TxB15jaSnVl+LqTn6YZ9EnygVuxjaVvR7GEPyglmN2g2IWE 1iRnqtvobbvjBMI8pTeyolQm1P6TlU23AHoMQ7IGoOeRMjO4G+Rx/4HusGybKfJa eUWIPwtKfxRXIRg+jdRAFnirp9wtvOUG2k/xKJ/+jq3b9PnC+TbVAyeMCRV/JkZL AWqSRxxOTKuCBCj79WamIaIoYQ1GKes41FtJa8nkJ5kBSB/jpRfliX/NCIhp2O9n y7S0VBa1G8pgsMoL3kxEhmK11KXsovrtm51A1V7tY8DdF5STzVf7lk9MX/vSy1G6 WYIjVBbmoKmFHUTRKZt+wlYiGsoyBAMo/iPZzprjLmRE2vDinmn8N+eSz+VZiLl1 ojRqOUqg9+t3VjRvxep/i7yMpT4Uk6mSpWu5tHJvmsDvhb408xw= =HROa -----END PGP SIGNATURE----- --nwz6r5hfgdqb5n7o--