C++ Notes: Array Initialization has a nice list over initialization of arrays. I have a
int array[100] = {-1};
expecting it to be full with -1's but its not, only first value is and the rest are 0's mixed with random values.
The code
int array[100] = {0};
works just fine and sets each element to 0.
What am I missing here.. Can't one initialize it if the value isn't zero ?
And 2: Is the default initialization (as above) faster than the usual loop through the whole array and assign a value or does it do the same thing?
Using the syntax that you used,
int array[100] = {-1};
says "set the first element to -1
and the rest to 0
" since all omitted elements are set to 0
.
In C++, to set them all to -1
, you can use something like std::fill_n
(from <algorithm>
):
std::fill_n(array, 100, -1);
In portable C, you have to roll your own loop. There are compiler-extensions or you can depend on implementation-defined behavior as a shortcut if that's acceptable.