C++ Primer, Fifth Edition

17.1.2. Using a tuple to Return Multiple Values

A common use of tuple is to return multiple values from a function. For example, our bookstore might be one of several stores in a chain. Each store would have a transaction file that holds data on each book that the store recently sold. We might want to look at the sales for a given book in all the stores.

We’ll assume that we have a file of transactions for each store. Each of these per-store transaction files will contain all the transactions for each book grouped together. We’ll further assume that some other function reads these transaction files, builds a vector<Sales_data> for each store, and puts those vectors in a vector of vectors:

// each element in files holds the transactions for a ...