Write a function named average_of_lines that accepts a file name as a parameter and reads that file, assumed to be full of real numbers,
and returns the average (mean) of the numbers in that file.
The parameter, $filename, gives the name of a file that contains a list of real numbers, one per line.
You may assume that the file exists and follows the proper format.
For example, if a file named input.txt contains the following numbers
1.5
2.75
9.0
-3.25
0.0
6.5
Then the call of average_of_lines("input.txt"); should return 2.75.
You may assume that the input file exists and is in the proper format.
If the file does not contain any input values, return 0.0.
Constraints:
Your solution should read the file only once, not make multiple passes over the file data.
