People skills? The informal prereqs/expected background for a class should be listed in the syllabus. Lack of "mathematical maturity" is a non-answer, they should make it clear what sort of math knowledge that refers to.
I disagree. 'Mathematical maturity', to me, means:
There is no specific advanced prerequisite knowledge, but you need to be able to follow something technical.
As an example: you'd reasonably expect a student with mathematical maturity to know what a set, the Cartesian product of two sets, and a function are. That's high school level math.
From there you can define a ring and a module over a ring, in like 5 mins.
So at that point the Prof, strictly speaking, told you everything you need to know to start studying modules.
Of course, many students will be like whaaaaaa?! When a ring is defined. But here's the point: Mathematical maturity does not mean that you already know what a ring is, but when the Prof defines a ring, you are following along.
Anyway, my point is that there is nothing specific that you need to know.
Mathematical maturity should be well defined if you are using it as a prerequisite. Mathematicians, of all people, should be good at coming up with such precise definitions.
Some people are better with math than others. Undergrad math majors thought the major was pretty easy. Many of us in engineering majors--who weren't that bad at math (it was a good school)--could no more have graduated with a degree in math (or physics) than have flapped our arms and flown.
Maybe the class did have pre-req? I mean i think it is obvious that a class called "Hard problems in combinatorial optimization" is aimed more at future Mathematicians/Computer Scientists than people who want to take it for the fun of it.
