<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>11 apr 2012 kl. 15.16 skrev Peter Kasson:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><blockquote type="cite">Date: Wed, 11 Apr 2012 14:33:09 +0200<br></blockquote><blockquote type="cite">From: Erik Marklund <<a href="mailto:erikm@xray.bmc.uu.se">erikm@xray.bmc.uu.se</a>><br></blockquote><blockquote type="cite">Subject: Re: [gmx-developers] Coordinate scaling in pdbio.c<br></blockquote>[...]<br><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">What happened to A2NM and NM2A?<br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">In my (4.0.5, yes that is very old) includes/physics.h I still see:<br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">#define A2NM (ANGSTROM/NANO) /* NANO */<br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">#define NM2A (NANO/ANGSTROM) /* 10.0 */<br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">Why aren't these still used for that?<br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">At some stage macros were removed from the code, even though these seem rather harmless. I agree that it is confusing to hard code these numbers. If we cannot use macro's like this we should probably replace them by<br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">static const real ANGSTROM=1e-10;<br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">static const real NANO=1e-9;<br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">etc.<br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">Comments?<br></blockquote></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">include/physics.h still has these macros. IMO, hard-coded constants are a greater evil than macros to prevent that, though I expect we will transition to const values at some stage soon.<br></blockquote></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite">But are these the kind of macros we want to avoid? Aren't function-like macros the ones to kill in the first place?<br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"> They're taking no parameters, so they're hardly function-like. The code fragments above are compiled into constants by the pre-processor. A macro that is used as<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">dist_in_nm = dist_in_angstrom * A2NM;<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">is much less evil than a macro<br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite">dist_in_nm = A2NM(dist_in_angstrom);<br></blockquote></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">My point exactly. I'm just not seeing the harm in using macros in cases like these.<br></blockquote><br>Consts are preferred (not #defines but actual consts).<br><br><a href="http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Preprocessor_Macros">http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Preprocessor_Macros</a><br></div></blockquote><div><br></div>Thanks. Ok, I have no wish defending macros in absurdum, but I still think that these macros are pretty harmless, except perhaps that the names A2NM and NM2A are potentially non-unique.</div><div><br><blockquote type="cite"><div>--<br>gmx-developers mailing list<br><a href="mailto:gmx-developers@gromacs.org">gmx-developers@gromacs.org</a><br>http://lists.gromacs.org/mailman/listinfo/gmx-developers<br>Please don't post (un)subscribe requests to the list. Use the<br>www interface or send it to gmx-developers-request@gromacs.org.<br></div></blockquote></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>-----------------------------------------------</div><div>Erik Marklund, PhD</div><div>Dept. of Cell and Molecular Biology, Uppsala University.</div><div>Husargatan 3, Box 596, 75124 Uppsala, Sweden</div><div>phone: +46 18 471 6688 fax: +46 18 511 755</div><div><a href="mailto:erikm@xray.bmc.uu.se">erikm@xray.bmc.uu.se</a></div><div><a href="http://www2.icm.uu.se/molbio/elflab/index.html">http://www2.icm.uu.se/molbio/elflab/index.html</a></div></div></span></div></span></span>
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