Behavior of Increment Operators

Please guide me what'll be output of the following code segment in c++ if 'a' is initialized at 7.

1	`cout<<a++<<a<<++a;`

Moderator's Note: This kind of questions actually have no answer. Here’s why. In practice, avoid them

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`2^{34}`	$2^{34}$
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Comments

The output should be $7 \quad 8 \quad 9$

When you use a++ operator it first prints the value of a then increments its value. so first the value of $a = 7$ gets printed then its value gets incremented to $8$ . After this when you use the ++a operator, it first increments the value of $a$ then prints it so first the value to a is increased to 9 then it is printed.

In short the post increment operator (a++) increments the value of a after the command given to it while the pre increment operator (++a) first increments the value of a then it is used in the command given to it.

Hope it helps :)

neelesh vij - 5 years, 3 months ago

I too thought of the same output but my compiler gave it out as '888'. Well, thank you for the views.

anweshan bor - 5 years, 3 months ago

Cascading cout statements are initialized from right to left. Though as Agnishom mentioned, this isn't a good idea, such questions commonly come for Viva.

Vishnu Bhagyanath - 5 years, 3 months ago

@Vishnu Bhagyanath – Well, it's worse than a bad idea. It is undefined.

Now that I am an ex-student, I should probably drop an email to our CS teacher.

Agnishom Chattopadhyay - 5 years, 3 months ago

@Agnishom Chattopadhyay – I asked this from my CS teacher and she said that the output depended on which compiler we are using. Different compilers could give different output. Is it so??

anweshan bor - 5 years, 3 months ago

@Anweshan Bor – Read up on the link Agnishom posted

Vishnu Bhagyanath - 5 years, 3 months ago

@Vishnu Bhagyanath – Actually the cascading took place from right to left as after postfix(++a) .It becomes the last updated value i.e 8 . So compiler starts reading the output from right to left.

tivansh verma - 5 years, 3 months ago

@Agnishom Chattopadhyay – Please cc to all Indian CS teachers.

Pranjal Jain - 5 years ago

@Pranjal Jain – Haha

Agnishom Chattopadhyay - 5 years ago

Actually, coding like this is ambiguous and considered a bad idea

Agnishom Chattopadhyay - 5 years, 3 months ago

Yes totally agreed.

neelesh vij - 5 years, 3 months ago

Answers explaining why this is not a good idea Quora and StackOverflow

@anweshan bor

Agnishom Chattopadhyay - 5 years, 3 months ago

The answer is : 7 8 8

Rashi Kashyap - 5 years, 3 months ago

Answer will be 888.

tivansh verma - 5 years, 3 months ago

You completely ignored what I said.

Agnishom Chattopadhyay - 5 years, 3 months ago

The answer is 888.. Bcoz cout has a right to left associativity... So the answer mostly depends on compailer...in right to left associative answer is 888...

Who Am I - 5 years, 2 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$