Adding average mean algorithm

maths/average_mean.mojo

@@ -0,0 +1,33 @@
+## Average mean
+
+fn mean(nums: List[Int]) raises -> Float64:
+    """
+    Find mean of a list of numbers.
+    Wiki: https://en.wikipedia.org/wiki/Mean.
+
+    Parameters:
+    - nums: A list of integers.
+
+    Returns:
+    - The mean of the list of numbers.
+
+    ```mojo
+    from testing import assert_almost_equal, assert_raises
+    from average_mean import mean
+    DELTA = 1e-6
+    assert_almost_equal(mean(List(5, 10, 15, 20, 25, 30, 35)), 20.0, atol=DELTA)
+    assert_almost_equal(mean(List(1, 2, 3, 4, 5, 6, 7, 8)), 4.5, atol=DELTA)
+    assert_almost_equal(mean(List(3, 6, 9, 12, 15, 18, 21)), 12.0, atol=DELTA)
+    with assert_raises():
+        var empty = List[Int]()
+        _ = mean(empty)
+    ```
+    """
+    if len(nums) == 0:
+        raise Error("List is empty")
+
+    var list_sum = 0.0
+    for num in nums:
+        list_sum += num[]
+
+    return list_sum / len(nums)