Problem
1. Write a function that will read the entries of a lower triangular table from the terminal. The entries should be of type double.
2. Write a function that will print a lower triangular table at the terminal.
3. Suppose that a lower triangular table is a table of distances between cities, as often appears on a road map. Write a function that will check the triangle rule: The distance from city A to city C is never more than the distance from A to city B, plus the distance from B to C .
4. Embed the functions of the previous projects into a complete program for demonstrating lower triangular tables.