TDD for functional programming

Programming in the 1950s was very different from what we know today. The job we now know as that of a programmer was split between three roles. The programmer would write the algorithm meant to be implemented. Then, a specialized typist would type it into punch cards using a special machine. The programmer then had to manually verify that the punch cards were correct—although there were hundreds of them. Once happy that the punch cards were correct, the programmer would take them to the mainframe operator. Since the only computers in existence were huge and very expensive, the time spent on the computer had to be protected. The mainframe operator took care of the computer, ensuring that the most important tasks took precedence, and thus a new program could wait for days until it was run. Once run, the program would print a full stack trace...