Date: Wed, 13 Jan 2016 17:52:25 -0500 From: Jon Radel <jon@radel.com> To: freebsd-questions@freebsd.org Subject: Re: dc(1) bugs Message-ID: <5696D529.9080901@radel.com> In-Reply-To: <slrnn9d8oc.d44.naddy@lorvorc.mips.inka.de> References: <0McVKy-1aajq60oIS-00Hgju@mail.gmx.com> <slrnn9d8oc.d44.naddy@lorvorc.mips.inka.de>
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This is a cryptographically signed message in MIME format. --------------ms090705000209070102000303 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable On 1/13/16 2:18 PM, Christian Weisgerber wrote: > Simpler examples: > > $ dc -e '50k 16i .1 p' > 0.0 > $ dc -e '50k 16i .10 p' > .06 > $ dc -e '50k 16i .100 p' > .062 > $ dc -e '50k 16i .1000 p' > .0625 > > I'll note that GNU dc(1) behaves the same way, so I think it is a > case of poorly documented or counter-intuitive behavior rather than > a bug. The man page makes clear, in a slightly muddy sort of way, that scale=20 set with the "k" operator can set limits on the scale of the output, but = is not deterministic. See the section on the ordinary arithmetic=20 operators. Base conversion, apparently, ignores the scale set with=20 "k". A bit clumsy, IMHO; for starters, 4 digits of precision in hex=20 isn't exactly 4 digits of precision base 10. Clumsy? Well, I'd think that $ dc -e '50k 16i .10 .1 + p' =2E06 $ should really output .12, but there is a certain logic to the answer it=20 does give if one assumes it converts base first and then adds. For an example where "k" does something: $ dc -e '3k 16i .10000 .10000 * p' =2E00390 $ dc -e '6k 16i .10000 .10000 * p' =2E003906 $ Bottom line? dc might not be the best tool for hex fractions. :-( --Jon Radel jon@radel.com --------------ms090705000209070102000303 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCC Cq8wggSvMIIDl6ADAgECAhEA4CPLFRKDU4mtYW56VGdrITANBgkqhkiG9w0BAQsFADBvMQsw CQYDVQQGEwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4 dGVybmFsIFRUUCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290 MB4XDTE0MTIyMjAwMDAwMFoXDTIwMDUzMDEwNDgzOFowgZsxCzAJBgNVBAYTAkdCMRswGQYD VQQIExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNP TU9ETyBDQSBMaW1pdGVkMUEwPwYDVQQDEzhDT01PRE8gU0hBLTI1NiBDbGllbnQgQXV0aGVu 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