*NaN*("Not a Number") to cover such cases. So they can now proudly write tan(90°)=

*NaN*and ln(-5)=

*NaN*and 0/0=

*NaN*etc. That's a nice and compact method for signalling a calculation "went off track".

If you get such a result in manual operation of your calculator, you may frown but usually know immediately what you did wrong. If, OTOH, such a result is returned by a routine, it may cost you some time and effort to find its origin - then you will try avoiding this "error" case in future by applying suitable means.

Now the question: Will you ever throw such a

*NaN*result into a subsequent calculation?

I.e. put something non-numeric into a numeric procedure? If true, why?

Of course you can, and I've seen some academic examples where this was done - but does anyone know a real-world problem where this turned out advantegeous or beneficial? (No computer science but down to earth, please.)

Thanks in advance for your answers!