Infix to Postfix. How to do this correctly?

Question

PS - This is not related to programming. I'm sorry, but I had a doubt and I wished to make a program for this, so...

I recently learned conversion of infix to postfix expressions. Thus a*(b+c) will be converted to abc+* using stacks. I made a program for the same and it works ( for many, but not all).

Consider a+b+c. Me and my program both generate the final expression as abc++. But on checking the net, I found that it was ab+c+.

Here is my approach to this :

https://code.sololearn.com/cvA1wSM5pSqh/?ref

Answer 1

from reading that article that krishna posted it would seem abc++ is correct, ab+c+ seems to be unnecessary (unless I am missing something) as order is always read left to right..

Answer 2

yeah best to do what the teacher wants

Answer 3

Once again you have exceeded my knowledge base. Wish I could help.

Answer 4

both are correct. but if she says to use "abc++" then use that. check your text book, ask some other professor then go with that.

while you may use "ab+c+" & may be even right, the person checking your exam paper may not know this is correct & may deduct marks or flat out mark it wrong( worst case scenario).

Answer 5

@Kinshuk Vasisht
do what works best for you.

i tried the online converter
this was the infix expression ((15 ÷ (7 − (1 + 1))) × 3) − (2 + (1 + 1)) i got this result 15 ÷ 7 − 1 1 + × 3 − 2 1 1 + +
but when i gave it in postfix-infix it shows it as invalid

Answer 6

@jay you are not alone here read the definition
http://www.cs.man.ac.uk/~pjj/cs212/fix.html

for more results: https://duckduckgo.com/?q=infix+and+postfix&t=h_&ia=web

Answer 7

@jay more read on polish notation or simple postfix
https://en.m.wikipedia.org/wiki/Reverse_Polish_notation

Answer 8

http://scanftree.com/Data_Structure/prefix-postfix-infix-online-converter

the previous example throws error on most converter's online.

another example
infix: 7+8*12/9
postfix: 7 8 12 * 9 / + //the operator multiplication was considered according to operator precedence.

Answer 9

Well, let me try a postfix to infix calculator now. That will clear my doubts.

If both yield a same answer, then Ill use abc++.
Else, Ill show them why it isn't abc++ (Ill convert it back to infix and display the result).

Answer 10

@Lord Krishna && @ jay
scanftree.com/Data_Structure/prefix-postfix-infix-online-converter
Checking both statements here makes me conclude that both are the same. Both yield a+b+c, and so Ill write according to the education board (After all, now I can' argue any more).

Answer 11

I have read more on this and found that :

The expression a+b+c is evaluated as (a+b)+c as the + operator is left to right associative. This is why the postfix comes out to be ab+c+ and this is useful in a-b-c.

But a+b+c is also equal to a+(b+c), then why isn't this used, and why is the associativity fixed like this?

I'm from India, and my teacher has told me to use only abc++, even when I explained to her the logic and the real answer comes out to be ab+c+. Her explanation was that this is what our education system wants and in the end, this will only fetch you marks...

What am I to do? Please explain me which is correct - abc++ or ab+c+ ?