Write a function named AverageValueInFile 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 AverageValueInFile("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.
