Can everything which can be done with "while" loops be done with "for" loops and vice versa?

Question

Is it true that, in C, we can do anything using while loop which can be done using for loop and vice versa?

Answer 1

Yes, except for definition of variables inside for

for (init; cond; incr) { body; }

If body does not contain a continue statement, the for statement above is completely equivalent to the while loop below.

init;
while (cond) {
    body;
    incr;
}

---

If you add an extra set of curly braces, even the definition of variables can be converted from for to while

for (int i = 0; i < 100; i++) { printf("%d\n", i); }

is the same as

{
    int i = 0;
    while (i < 100) {
        printf("%d\n", i);
        i++;
    }
}

Answer 2

Yes, a for loop can be constructed with a while loop.

{   int i = 0;
    while(i < 10){
// statement block without continue.
        ++i;
    }
}

and a for loop can replace a while loop trivially by omitting the init and increment sections.

This doesn't mean it's a good idea. They have different semantics. The for loop is used to iterate over a given set of elements, i.e.

for(auto e: collection)...

while is used for other non counting iterations.

Answer 3

Yes, it can be used vice-versa. But for a code to be more readable, its wise to use the appropriate one.

while loop usage : loop until a condition is met. the condition is met due to the actions inside the loop.

for loop usage : loop until a condition is met. Here the condition is met be more or less increment/decrement operator present in for loop syntax iteself.