Reading through this classic paper, I’m stuck on paramorphisms. Unfortunately the section is quite thin, and the Wikipedia page doesn’t say anything.

My Haskell translation is:

```
para :: (a -> [a] -> b -> b) -> b -> [a] -> b
para f base = h
where
h [] = base
h (x:xs) = f x xs (h xs)
```

But I don’t grok that — I don’t have any intuition for the type signature or the desired result.

What’s a paramorphism, and what are some useful examples in action?

Yes, I’ve seen these questions, but they don’t cover paramorphisms directly and only point to resources that may be helpful as references, but not as learning materials.

### More Related Questions

- How to move a subtree between trees in Haskell? For two multi-way trees, t1 and t2, defined using
type Forest a = [Tree a]
data Tree a = Node {
rootLabel :: a,
subForest :: Forest a
}
how can I write a […]
- Higher-order function, parse error on input `| Here is my code:
select_where_true :: (Double -> Bool) -> [Double] -> [Double]
select_where_true is_neg [a] = case [a] of
[] -> []
x:xs -> is_neg x
|(is_neg […]
- How can a time function exist in functional programming? I've to admit that I don't know much about functional programming. I read about it from here and there, and so came to know that in functional programming, a function returns the same […]
- Haskell function application and currying I am always interested in learning new languages, a fact that keeps me on my toes and makes me (I believe) a better programmer. My attempts at conquering Haskell come and go - twice so far […]
- How do functors work in haskell? I'm trying to learn Haskell and I'm through all the basics. But now I'm stuck, trying to get my head around functors.
I've read that "A functor transforms one category into another […]
- "What part of Milner-Hindley do you not understand?" I can't find it now, but I swear there used to be a T-shirt for sale featuring the immortal words:
What part of
do you not understand?
In my case, the answer would be... all of […]
- Write a Haskell interpreter in Haskell A classic programming exercise is to write a Lisp/Scheme interpreter in Lisp/Scheme. The power of the full language can be leveraged to produce an interpreter for a subset of the […]
- What is tail-recursion? Whilst starting to learn lisp, I've come across the term tail-recursive. What does it mean? Asked By - Ben Lever Read Answers
- Partial Application with Infix Functions While I understand a little about currying in the mathematical sense, partially
applying an infix function was a new concept which I discovered after diving
into the book Learn You a […]
- Haskell – specifying kind in data declaration In this declaration
data Const a = Const Integer
Haskell infers that Const is * -> *. Is it possible to make Const take a type constructor instead, so it will be (* -> *) -> *? […]