Jump to content
  • Advertisement
Sign in to follow this  
arithma

Problem with understanding Operators

This topic is 4612 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

My C++ instructor has recently been explaining the unary prefix and postfix operators (mainly ++ and --) It shows out that: ++a + ++a is equivalent to (++a, ++a, a + a) so if a = 1 it returns 6 I tried it on Borland and VC++6.0 and it worked as he said However I thought it would return 5, as in it adds one to a, (a=2), it adds one to the next a (a=3) so the expression will be 5 ++a + ++a ++1 + ++a 2 + ++a 2 + ++2 2 + 3 5 Am desperate, and I know it has to do with precedence

Share this post


Link to post
Share on other sites
Advertisement
Quote:
Original post by arithma
Am desperate, and I know it has to do with precedence

Speaking strictly from an operator precedence point of view, pre-increment has higher precedence than addition, so both increments will be done before the addition. Where things get really weird is with post-increment: what are the values of a and b after the following statements?
int b, a = 1;
b = a++ + a++;


This is why some languages don't have increment operators, like Python.

Share this post


Link to post
Share on other sites
The replies are still inconclusive: who is right
Does ++a + ++a have a defined behavior indorsed by the standard, or is it left to the compiler to decide upon it

Share this post


Link to post
Share on other sites
Quote:
Original post by arithma
The replies are still inconclusive: who is right


What do you mean? Only one person has posted about this.

Share this post


Link to post
Share on other sites
Ooops,
I didn't see that the same person was posting as I rushed into viewing the reply

However, can I conclude that the standard doesnot impose the order-of-precedence point-of-view?

Share this post


Link to post
Share on other sites
Quote:
Original post by arithma
Ooops,
I didn't see that the same person was posting as I rushed into viewing the reply

However, can I conclude that the standard doesnot impose the order-of-precedence point-of-view?


Since the + operator is not a sequence point, the operands could be evaluated in any order.

Share this post


Link to post
Share on other sites
Quote:
Original post by arithma
However, can I conclude that the standard doesnot impose the order-of-precedence point-of-view?

It has nothing to do with order of operations. As Oluseyi has stated, multiple modifications of a single variable in between sequence points is undefined. It's not supported by the standard, and is compiler-implementation defined.

Read more about it here.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

Participate in the game development conversation and more when you create an account on GameDev.net!

Sign me up!