It won't. If any of the functions on the right-hand side of the '<-' return Nothing, then the later lines do nothing. Think of the '<-' operator as a 'flatMap'

It won't. If any of the functions on the right-hand side of the '<-' return Nothing, then the later lines do nothing. Think of the '<-' operator as a 'flatMap' call for Optionals in Java, if you are more familiar with that. This particular syntax for chaining together monads is called 'do notation', and is just syntax sugar for calling the bind function (flatMap in Java) manually.