Composing functions together with the pipe operator

The Unix operating system's command line shell allows the standard output of one function to be piped into the another to form a filter chain. Later, this feature became part of every command line shell offered as part of most operating systems. While writing functional style code, when we combine methods through functional composition, the code becomes hard to read because of deep nesting. Now, with Modern C++ we can overload the pipe (|) operator to allow chaining several functions together, like we do commands in a Unix shell or Windows PowerShell console. That is why someone re-christened the LISP language as Lots of Irritating and Silly Parentheses. The RxCpp library uses the | operator extensively to compose functions together. The following code helps us understand how one can create pipeable functions. We will...