c - What does an assignment return?

Question

Why does an expression i = 2 return 2? What is the rule this is based on?

printf("%d ", i = 2 ); /* prints 2 */

I am in C domain after spending long time in Java/C#. Forgive my ignorance.

question from:https://stackoverflow.com/questions/9514569/what-does-an-assignment-return

Answer 1

It evaluates to 2 because that's how the standard defines it. From C11 Standard, section 6.5.16:

An assignment expression has the value of the left operand after the assignment

It's to allow things like this:

a = b = c;

(although there's some debate as to whether code like that is a good thing or not.)

Incidentally, this behaviour is replicated in Java (and I would bet that it's the same in C# too).