This is the 15th post in the Exercises in Programming Style focus series. Last week, we solved the top 25 word frequencies problem with the help of the database. This week, we will get back to solve it with code alone. The design is to model the problem as a spreadsheet. The spreadsheet holds a number of cells, each cell having a value and a formula. Just like in regular spreadsheet, the formula is a function that might reference another cell’s value, and computes the current cell’s v