Stop pretending studying arrow theory improves your apping

Given two functors S,T:C→B, a natural transformation τ:S→T is a function which assigns to each object c of C an arrow τ_c=τc:Sc→TC of B in such a way that every arrow f:c→c' in C yields a diagram
ﾠﾠﾠﾠﾠﾠﾠﾠﾠﾠﾠτc
c ﾠﾠ Sc---→Tc
|ﾠﾠﾠﾠﾠﾠﾠﾠ|ﾠﾠﾠﾠﾠﾠﾠ|
|fﾠﾠﾠﾠﾠSf↓ﾠﾠﾠﾠﾠ↓Tf
↓ﾠﾠﾠﾠﾠﾠﾠ|ﾠﾠτc'ﾠﾠ|
c', ﾠﾠﾠ Sc'--→Tc'

which is commutative. When this holds, we also say that τ_c=τc:Sc→Tc is natural in c. If we think of the functor S as giving a picture in B of (all the objects and arrows of) C, then a natural transformation τ is the set of arrows mapping (or, translating) the picture S to the picture T, with all squares (and parallelograms!) like that above commutative:
ﾠaﾠﾠﾠﾠﾠﾠﾠﾠﾠﾠSa----------→Ta
ﾠ|ﾠ╲fﾠﾠﾠﾠﾠﾠﾠ ﾠ|ﾠ╲Sfﾠﾠﾠﾠﾠﾠﾠﾠﾠ|ﾠ╲Tf
ﾠ|ﾠﾠﾠ↘ﾠﾠﾠﾠﾠﾠﾠ|ﾠﾠﾠ↘ﾠﾠﾠτbﾠﾠﾠ|ﾠﾠﾠ↘
ﾠ|ﾠﾠﾠﾠﾠbﾠﾠﾠﾠ ﾠ|ﾠﾠﾠﾠSb----------→Tb
ﾠ|ﾠﾠﾠ╱ﾠﾠﾠﾠﾠﾠﾠ|ﾠﾠﾠ╱ﾠﾠﾠﾠﾠﾠﾠﾠﾠ|ﾠﾠﾠ╱
↓ﾠ↙ﾠﾠﾠﾠﾠﾠ ﾠ↓↙Sgﾠﾠﾠﾠﾠﾠﾠﾠ↓ﾠ↙Tg
ﾠcﾠﾠﾠﾠﾠﾠﾠﾠﾠﾠSc----------→Tc

>>48
Pure finance is one of those sectors where you'll be hard-pressed to convince people that it actually counts as being in production. It's one thing to have running code that does something, but just like academia, that "something" is purely representative and not actually useful or meaningful to what happens in real life. The financial sector as we know it today is 90% sleight of hand, lying to people and passing money around in a shell game to hide it from your own "customers." It's the same thing Hollywood has been doing since the 1930s to invent massive profits and pay none of the costs, only this time the public doesn't even get anything back as a side effect of their dirty lies.

Haskell, as a language, is of exactly the same character, so it's perfectly suited to the thieves and circus clowns in the financial sector. A real programmer wouldn't touch it with a ten foot pole.