What does it mean when the first “for” parameter is blank?

Question

I have been looking through some code and I have seen several examples where the first element of a for cycle is omitted.

An example:

for ( ; hole*2          


        

Answer 1

Some people have been getting it wrong so I just wanted to clear it up.

int i = 0;
for (; i < 10; i++)

is not the same as

for (int i = 0; i < 10; i++)

Variables declared inside the for keyword are only valid in that scope.

To put it simply.

Valid ("i" was declared outside of the loops scope)

int i = 0;
for (; i < 10; i++)
{
  //Code
}
std::cout << i;

InValid ("i" does not exist outside the loop scope)

for (int i = 0; i < 10; i++)
{
  //Code
}
std::cout << i;