GADTs, phantom types, and arrows (not to mention monad transformers) aren't "mathematical terms" in that the names aren't borrowed from mathematical terminology.
They're just _terms_. But to you they are new terms. So you call them "mathematical terms" because obviously if you haven't heard of it, then it must be complicated math.
It isn't.
If you stop thinking that every new concept you meet in the world (or at least in Haskell) is a "mathematical concept" and start thinking it is "just a thing that is new and I can learn" then maybe you will stop feeling this way.
For that matter, none of the things you list except for Functors and Monad Transformers (which are just "ways to build monads") are idiomatic for "basic" haskell programming, and the next step up, GADTs is a straightforward feature to learn when you need.
If you read something like RWH or LYAH, you'll notice they don't cover arrows or GADTs that much. That's because they're not considered core concepts. If you set out to learn "all the things" and then discover that there are a lot of things, perhaps the problem is just that you set out to learn "all the things" under the false impression that you need to in some immediate way.
They're just _terms_. But to you they are new terms. So you call them "mathematical terms" because obviously if you haven't heard of it, then it must be complicated math.
It isn't.
If you stop thinking that every new concept you meet in the world (or at least in Haskell) is a "mathematical concept" and start thinking it is "just a thing that is new and I can learn" then maybe you will stop feeling this way.
For that matter, none of the things you list except for Functors and Monad Transformers (which are just "ways to build monads") are idiomatic for "basic" haskell programming, and the next step up, GADTs is a straightforward feature to learn when you need.
If you read something like RWH or LYAH, you'll notice they don't cover arrows or GADTs that much. That's because they're not considered core concepts. If you set out to learn "all the things" and then discover that there are a lot of things, perhaps the problem is just that you set out to learn "all the things" under the false impression that you need to in some immediate way.