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

Note by Anweshan Bor
2 years, 7 months ago

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

Agnishom Chattopadhyay Staff - 2 years, 7 months ago

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Yes totally agreed.

Neelesh Vij - 2 years, 7 months ago

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

@anweshan bor

Agnishom Chattopadhyay Staff - 2 years, 7 months ago

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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 - 2 years, 7 months ago

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

Anweshan Bor - 2 years, 7 months ago

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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 - 2 years, 7 months ago

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@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 Staff - 2 years, 7 months ago

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@Agnishom Chattopadhyay Please cc to all Indian CS teachers.

Pranjal Jain - 2 years, 4 months ago

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@Pranjal Jain Haha

Agnishom Chattopadhyay Staff - 2 years, 4 months ago

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@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 - 2 years, 7 months ago

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@Anweshan Bor Read up on the link Agnishom posted

Vishnu Bhagyanath - 2 years, 7 months ago

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@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 - 2 years, 7 months ago

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The answer is : 7 8 8

Rashi Kashyap - 2 years, 7 months ago

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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 - 2 years, 7 months ago

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Answer will be 888.

Tivansh Verma - 2 years, 7 months ago

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You completely ignored what I said.

Agnishom Chattopadhyay Staff - 2 years, 7 months ago

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