Question

I had the following code in a test.I am confused about what (i,j) evaluates,while reading about the “,” operator i found that it just evaluates the variables or functions but what does it do here?

main()
{
    int i = 10, j = 20;

    j = i ? (i, j) ? i : j : j;
    printf("%d %d", i, j);
}

Answer 1

The comma operator can be used to link the related expressions together. A comma-linked list of expressions is evaluated left-to-right and the value of the rightmost expression is the value of the combined expression. It acts as a sequence point.

A sequence point guarantees that all side effects of previous evaluations will have been performed, and no side effects from subsequent evaluations have yet been performed.

So, any expression/assignment will be completed & only then will the next expression to the right be evaluated.

For example,

b=(a=4,a=5);

gives,

a=5
b=5

Also, note that the comma operator ranks last in the precedence list of operators in C.