How to read the expression (i = j) || (j = k)

I was practicing some exercise from the book, so I wrote down the program below.

Code:

---

#include<stdio.h>

int main(void)
{
    int i = 7, j = 8, k = 9;
   
    printf("%d ", (i = j) || (j = k));
    printf("%d %d %d", i, j, k);
   
    getch();
    return 0;
}

---

The result should be 1 8 8 9, but I don't know how this expression work.
How to interpret the expression (i = j) || (j = k)?
In the first parentheses (i = j), did the program assign 8 to i?
If so, why didn't it assign 9 to j as well, in the second parentheses (j = k)?
Later on, why the i remain as 8, when was it saved?

Ok, this is about the way C evaluates logical or ...

It will look at (i = j) || (j = K) only far enough to decide if one OR the other is true... left to right i = j will assign the value of j to i ... this will always result in true, so it never tests the second set of braces and thus never assigns j = k.

The I will remain 8 because you used assignment (single equal sign) not comparison (double equal sign). That is to say that ...

Code:

---

if (i = j)
 printf ("Hello");

---

... assigns the value of j to i and will always be true (because it succeeded) and it will always print "Hello".

However...

Code:

---

if (i == j)
 printf("Hello");

---

... only if the value of i is the same as the value of j ... neither value is changed.

Try your original code with double equals ( == ) in that first printf() call ... it should print 1789 instead.

Why is i = j will always be true?

Quote:

---

Originally Posted by Roger Lo

Why is i = j will always be true?

---

It's a standard set by ANSI C. Anything not 0 is true. This world is full of standards and conventions which sometimes make sense, sometimes don't.

> ... assigns the value of j to i and will always be true (because it succeeded) and it will always print "Hello".
It only succeeds because j is non-zero.
If j was zero, then the assignment would still happen, but the logical side effect (the implied (expr) != 0) is false.

Quote:

---

Originally Posted by Roger Lo

Why is i = j will always be true?

---

See Salem's post... I should qualify my statement to say that "in your example" it will always be true.
As Salem points out, if j is 0, it will evaluate to false...
Another way of breaking it down to understand it is...

Code:

---

i = j;
if ( i != 0 )
  Printf("Hello");

---

understood, thanks for everyone!