Reverse Polish Notation (RPN)

Discus: Individual Schools: US News Top 25: Massachusetts Institute of Technology: 2004 Archive: Reverse Polish Notation (RPN)
 By Whizkid (Whizkid) on Wednesday, May 19, 2004 - 04:14 am: Edit

All HPs use RPN. Does our mind also think in RPN ??? For example, when we are asked to do 3 + 5, the plus sign comes to our mind first or the number.

 By Wintermute (Wintermute) on Wednesday, May 19, 2004 - 08:45 pm: Edit

Interesting concept. Now that you mention it, the plus sign does seem to stick out...but then again, I remember being in the second grade and getting terrible grades on those stupid "time tests" where they see how many simple addition and/or subtraction problems you can do in 2 munites, because I kept mixing up the addition and subtraction. Maybe the way you look at it changes with age or experience...

Not to hijack your thread or anything, but on that note, does MIT suggest/require students to use an HP or a TI graphing calculator?

 By Gottagetout (Gottagetout) on Wednesday, May 19, 2004 - 09:21 pm: Edit

Not only do all HPs use RPN, many other calculators and computers do too!

I don't think you can generalize to the entire human race and say that we use RPN for mental math. Instead, I think it might be used by some people but probably not often. For instance, with 3 + 5, I would take 3 and add 5 to it. I would not think: 3, 5, add. This is mainly because it yields little benefit to us, as humans, because we do not operate using a stack.

Also, even with RPN, the number would come first because RPN is postfix

 By Whizkid (Whizkid) on Thursday, May 20, 2004 - 03:36 am: Edit

Wintermute: It's personal preference. I've been using HP 48G+ since 12th grade and recently I had to borrow someone's TI. I had a hard time punching equations in! It's annoying when you have to take care of all the brackets. With an HP,you can just work inside out without bothering with the brackets.

Gottagetout: You theory sounds logical but let's go back to 2nd grade math. You have 3 apples, I give you 5 more. How many apples do u have now? In this situation, you will see 3, 5, add. That's RPN. But when they actually make you add them on paper, It's not.
3
+5
---
8
---

 By Mrowry (Mrowry) on Thursday, May 20, 2004 - 04:57 pm: Edit

I see 5 and add 3... does that make a difference?

 By 08beaver (08beaver) on Thursday, May 20, 2004 - 05:15 pm: Edit

I think my mind works in prefix notation. I see + first, then "combine" 3 and 5. It's like I see "+" which puts my mind in addition mode, and then I think that the combination of 3 and 5 makes 8.

 By Gottagetout (Gottagetout) on Friday, May 21, 2004 - 06:23 pm: Edit

Even with your example, it is not RPN. You say I have three apples and then you _give_ me five apples. I think "OK, three apples and I get (+) 5 more, so 8". I could see, however: "You have three apples, five apples are added." That seems to be RPN and does indeed make me think in RPN. However, I don't think this is the default mode for most humans. Default is probably prefix notation or just how you would right it (function with a lhs and rhs). Mental math using RPN incurs no benefits as I see it.

 By Jarchivist (Jarchivist) on Sunday, June 06, 2004 - 06:18 pm: Edit

Just in case this is actually on-topic: Many MIT classes don't let you use calculators on exams. On p-sets, use whatever you feel like.