[zelphirkalt]

I almost fully agree. A professional programmer, how can such a person not know about stuff like map, filter and reduce? It can only happen, when they never cared to learn programming languages, paradigms or concepts of various kinds. This would betray an attitude of not continuing to learn. Even, if they have not come into contact with other programming concepts, how can any professional not have heard anything about map-reduce stuff at some point somewhere? Seems very unlikely to happen without learning-resistance or disinterest towards learning or informing oneself.

However, I would exclude junior software developers from this, as they might have just come from university, where they might not have learned about this at all, depending on the university. Still computer programming is then what they do as "profession", so we would have to count them as "professionals".