# Not Backus-Naur Form **URL:** \ **Category:** Factual Questions\ **Created:** [September 27, 2016, 2:36pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038 "2016-09-27T14:36:43Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Cartoonacy](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@Cartoonacy](https://boards.straightdope.com/u/Cartoonacy)\ **Post date:** [September 27, 2016, 6:25pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/21 "2016-09-27T18:25:34Z")
Thanks, all. Now that I see it, it comes back to me. It’s been so long since I’ve had to use either one, I got the terms mixed up. I just started learning PostScript, which uses RPN, which is what brought it to mind. It’s probably _because_ we used to call it “Backwards is Normal Form” in school that I confused it with Reverse Polish Notation. ---
**Author:** ![Cartoonacy](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@Cartoonacy](https://boards.straightdope.com/u/Cartoonacy)\ **Post date:** [September 27, 2016, 6:29pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/22 "2016-09-27T18:29:32Z")
> [@CookingWithGas](#): > > I was in college studying computer science 38 years ago and your memory just committed a hardware fault. 😉 😃 ---
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [September 27, 2016, 6:43pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/23 "2016-09-27T18:43:14Z")
> [@naita](#): > > All the cool kids had RPN-calculators when I studied engineering 20 years ago. I bought my HP 16C scientific calculator in 1982. It still sits on my desk in its little wooden stand. I use it nearly daily, albeit mainly for simple addition and subtraction. How many other electronic gizmos still work perfectly, and usefully, after 34 years? I have a terrible time using a conventional calculator - the RPN has seeped into my bones. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [September 27, 2016, 7:32pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/24 "2016-09-27T19:32:19Z")
> [@Duke\_of\_Rat](#): > > I’ve had my HP 11C for 30 years! Damn, I hadn’t thought about when I bought that thing in a while. > > I was SA to the head of the math department, she looked sideways at us geeks with RPN calculators, she was a TI fan. So she’d make up complex (only algebra level stuff) equations and we’d race, her TI vs my HP. And I could beat her about half the time. > > Are RPN calculators still popular with geeks in school these days? I had an HP 11c in college decades ago but then lost it a few years after school. But then a few years ago, HP announced a special anniversary edition of the calculator, which I bought (for around $200, I think). Note that the original calculator was not cheap. I think I paid at least $200-300 for it in 1985. And we also had races between RPN calculators and ones doing algebraic notation. We were such nerds. (Those using the RPN calculators won every time of course.) ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [September 27, 2016, 11:12pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/25 "2016-09-27T23:12:06Z")
> [@friedo](#): > > Yes, you’ve confused BNF for RPN. > > Maybe because a common computer science exercise is to make a RPN calculator in a stack-based language like Forth, which would be described with BNF. That would be overkill; it’s easy enough to describe an infix syntax for mathematical operations using BNF, so that’s what’s done in every Baby’s First BNF Example I’ve seen. This is done in _The Unix Programming Environment_ to introduce yacc and lex, for example. Anyway, few enough people use strict BNF anyway; EBNF (Extended BNF), which is more convenient, is what’s actually implemented by most compiler-compilers. And, while we’re all talking about RPN calculators, I still have and cherish an HP-48GX which saw me through most of high school and all of college. ---
**Author:** ![Ace309](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ace309/32/1050_2.png) [@Ace309](https://boards.straightdope.com/u/Ace309)\ **Post date:** [September 27, 2016, 11:25pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/26 "2016-09-27T23:25:14Z")
It’s some kind of [sausage](https://xkcd.com/645/). ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [September 27, 2016, 11:37pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/27 "2016-09-27T23:37:46Z")
> [@ftg](#): > > (Then came Bison which in turn inspired the name GNU, if you wanted to know where that came from.) > [@markn\_1](#): > > I don’t think so. The GNU project started in 1983. Bison was written in 1988. Yep, GNU came first. The GNU acronym comes from GNU is Not Unix. It’s one of those silly recursive acronyms from the 80s, like PINE (Pine is Not Elm, though at some point it got officially changed to Pine Internet News and Email). ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [September 28, 2016, 12:18am UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/28 "2016-09-28T00:18:25Z")
> [@engineer\_comp\_geek](#): > > Yep, GNU came first. The GNU acronym comes from GNU is Not Unix. It’s one of those silly recursive acronyms from the 80s, like PINE (Pine is Not Elm, though at some point it got officially changed to Pine Internet News and Email). Since this thread is now thoroughly [del]pizzled[/del] hijacked, I might as well mention that the GNU Project’s perpetually-unready Official Kernel is called HURD, which stands for “HIRD of Unix-Replacing Daemons”, and HIRD stands for “HURD of Interfaces Representing Depth”. Yep: A pair of mutually-recursive acronyms. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 28, 2016, 12:31am UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/29 "2016-09-28T00:31:54Z")
Heh, I was just telling a student a couple of hours ago that I wasn’t sure how some of the functions on his TI worked, because I’m more familiar with HP, and HP is better once you learn to use them, but unfortunately they haven’t made any calculators in years. And my primary calculator is an HP48 emulator on my phone. All the RPN stack goodness, but it fits in my pocket easier, and it’s faster. ---
**Author:** ![IT\_Guy](https://avatars.discourse-cdn.com/v4/letter/i/3ec8ea/32.png) [@IT\_Guy](https://boards.straightdope.com/u/IT_Guy)\ **Post date:** [September 28, 2016, 3:32am UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/30 "2016-09-28T03:32:12Z")
> [@Chronos](#): > > Heh, I was just telling a student a couple of hours ago that I wasn’t sure how some of the functions on his TI worked, because I’m more familiar with HP, and HP is better once you learn to use them, but unfortunately they haven’t made any calculators in years. > > And my primary calculator is an HP48 emulator on my phone. All the RPN stack goodness, but it fits in my pocket easier, and it’s faster. Just as a note; [HP-35s](https://www.amazon.com/HP-F2215AA-ABA-Scientific-Calculator/dp/B000TDRHG8/ref=sr_1_1?ie=UTF8&qid=1475033348&sr=8-1&keywords=hp35s) and [HP-50g](https://www.amazon.com/HP-HP50G-50g-Graphing-Calculator/dp/B000GTPRPS/ref=sr_1_3?ie=UTF8&qid=1475033348&sr=8-3&keywords=hp35s). ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [September 28, 2016, 7:13am UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/31 "2016-09-28T07:13:43Z")
> [@Duke\_of\_Rat](#): > > Are RPN calculators still popular with geeks in school these days? Not that I know. Any decent calculator today allows you to type in the actual equation or expression in full. And if you have access to a computer you can do that in wolfram alpha without even needing a separate program. What kind of hoops they make you jump through on engineering exams around the world to show you understand the math without the help of professor google I don’t know. There might be schools where they rent out 20 year old RPN calculators. 😃 ---
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [September 28, 2016, 1:03pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/32 "2016-09-28T13:03:38Z")
I bought my HP 16C in 1982 for $120 - According to Google, that’s equivalent to $301 today. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 28, 2016, 1:05pm UTC](https://boards.straightdope.com/t/not-backus-naur-form/767038/33 "2016-09-28T13:05:51Z")
But “typing in the actual equation or expression in full” usually takes a lot more keystrokes than RPN. Even my preferred ancient HP 48s had a way to do that, and it was easier to use than most other equation editors I’ve seen (even ones that had the advantage of a mouse), and it _still_ hardly ever got used, because RPN was quicker. [Previous page](https://boards.straightdope.com/t/not-backus-naur-form/767038.md?page=1)