It's easy to fill up an array using for loop:
ulong[] chessArray = new ulong[64];
chessArray[0] = 1;
for (int i = 1; i < 64; i++)
{
chessArray[i] = 2 * chessArray[i - 1];
}
But is there a way to do it using foreach operator? The following code won't compile:
ulong[] chessArray = new ulong[64];
chessArray[0] = 1;
foreach (int element in chessArray)
{
element = 2 * (element - 1);
}
is there a way to do it using foreach operator?
No. The loop variable element is a read-only variable that contains a copy of the value of the array element, which is a variable. It is not an alias to the array element variable.
It is not possible to modify the array you are iterating using foreach, check this link : https://msdn.microsoft.com/en-us/library/ttw7t8t6.aspx
Why foreach? Your goal is to fill an array, in which each element's value is based on previous one. Clojure natively support such sequence creation by iterate.
(take 10 (iterate (partial * 2) 1)) //(1 2 4 8 16 32 64 128 256 512)
Notice the integer overflow if you want to take 64.
The same idea can apply to C#. (Please tell me if there is already an Iterate function).
public static IEnumerable<T> Iterate<T>(Func<T, T> f, T seed)
{
var val = seed;
while (true)
{
yield return val;
val = f(val);
}
}
Then you can fill an array by
Iterate(i => i * 2, (ulong)1).Take(64).ToArray()
Enumerable has Aggregate but not Iterate. Nice solution.The other answers and comments already show nicely that you cannot write to the loop variable in a foreach loop. However, even if this was possible, the two loops in the question would not do the same thing:
You cannot access the previous value of the loop variable by element - 1! Instead this will simply subtract one from the current variable before it is doubled. The result is completely independent of the previous value.
I.e. your foreach loop would correspond to 2 * chessArray[i] - 1; in the for loop.
for