<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Is moving to snake_case and the resulting inconsistency in the naming conventions worth the benefits? A wholesome change is out of the question.<div class=""><br class=""></div><div class="">Amara<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 1 Feb 2019, at 06:20, Michael Platings via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(255, 255, 255); color: rgb(255, 255, 255); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi all,<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">As application of the naming rules are currently under discussion [1] this seems like a good time to bring this up:<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">The current variable naming rule [2] states: Variable names should be nouns (as they represent state). The name should be camel case, and start with an upper case letter (e.g. Leader or Boats).<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">I'm a relatively new arrival to the LLVM codebase and I want to follow the rules wherever I can, but I humbly submit that this rule is suboptimal for readable code.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">The rationale given at the time this rule was added was "document the prevailing convention" [3]. It was debated after the policy change whether this was the right choice [4].<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">The main problem I find with this rule is that it is the same as the type naming rule. Why is this a problem? It is famously hard to name things ("There are 2 hard problems in computer science: cache invalidation, naming things, and off-by-1 errors.") and with this rule if you've already used a name for a type, you can't reuse it for a variable of that type.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">So what do you do instead? Often it seems the answer is to use an acronym (Target T), which hurts readability, or prepend "The" to the type name (Target TheTarget), which wastes space and also hurts readability because the start and end of a word are the most important for readnig. [5]<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">So we've got declarations like "LB(L, PSE, LI, DT, TLI, TTI, AC, ORE, VF.Width, IC, &LVL, &CM)" [6] which is quite intimidating to newcomers.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">If we could also use snake_case variable names then straight away you have an obvious, readable name (Target target). It looks like there's plenty of code that does this already, and it's consistent with our Python code. Also, it makes C idioms like "for (int i = 0; ..." permissible.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">I realize that there's also a rule [2] "Avoid abbreviations unless they are well known" - I believe allowing a trivial way to get readable names would help greatly to adhere to this.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">What do you think? Could we relax the variable naming rule?<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[1]<span class="Apple-converted-space"> </span><a href="http://lists.llvm.org/pipermail/cfe-dev/2019-January/061085.html" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">http://lists.llvm.org/pipermail/cfe-dev/2019-January/061085.html</a><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[2]<span class="Apple-converted-space"> </span><a href="https://llvm.org/docs/CodingStandards.html#name-types-functions-variables-and-enumerators-properly" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">https://llvm.org/docs/CodingStandards.html#name-types-functions-variables-and-enumerators-properly</a><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[3]<span class="Apple-converted-space"> </span><a href="https://github.com/llvm/llvm-project/commit/30e697ebaf4fc8a9b8cf6abecbc75ef1b9fa0dc0" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">https://github.com/llvm/llvm-project/commit/30e697ebaf4fc8a9b8cf6abecbc75ef1b9fa0dc0</a><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[4]<span class="Apple-converted-space"> </span><a href="http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20110808/126097.html" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20110808/126097.html</a><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[5] Mostly based on my own experience, but somewhat supported by evidence:<a href="https://en.wikipedia.org/wiki/Transposed_letter_effect" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">https://en.wikipedia.org/wiki/Transposed_letter_effect</a><o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">[6]<span class="Apple-converted-space"> </span><a href="https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp#L7433" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp#L7433</a><o:p class=""></o:p></div></div><span style="caret-color: rgb(255, 255, 255); color: rgb(255, 255, 255); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none; 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