Check array position for null/empty
There is no bound checking in array in C programming. If you declare array as
int arr[50];
Then you can even write as
arr[51] = 10;
The compiler would not throw an error. Hope this answers your question.
You can use boost::optional
(or std::optional
since C++17), which was developed in particular for decision of your problem:
boost::optional<int> y[50];
....
geoGraph.y[x] = nums[x];
....
const size_t size_y = sizeof(y)/sizeof(y[0]); //!!!! correct size of y!!!!
for(int i=0; i<size_y;i++){
if(y[i]) { //check for null
p[i].SetPoint(Recto.Height()-x,*y[i]);
....
}
}
P.S. Do not use C-type array -> use std::array or std::vector.
std::array<int, 50> y; //not int y[50] !!!
If the array contains integers, the value cannot be NULL. NULL can be used if the array contains pointers.
SomeClass* myArray[2];
myArray[0] = new SomeClass();
myArray[1] = NULL;
if (myArray[0] != NULL) { // this will be executed }
if (myArray[1] != NULL) { // this will NOT be executed }
As http://en.cppreference.com/w/cpp/types/NULL states, NULL is a null pointer constant!
If your array is not initialized then it contains randoms values and cannot be checked !
To initialize your array with 0 values:
int array[5] = {0};
Then you can check if the value is 0:
array[4] == 0;
When you compare to NULL, it compares to 0 as the NULL is defined as integer value 0 or 0L.
If you have an array of pointers, better use the nullptr
value to check:
char* array[5] = {nullptr}; // we defined an array of char*, initialized to nullptr
if (array[4] == nullptr)
// do something