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

The for construct is basically ( pre-loop initialisation; loop termination test; end of loop iteration), so this just means there is no initialisation of anything in this for loop.

You could refactor any for loop thusly:

pre-loop initialisation
while (loop termination test) {
...
end of loop iteration
}