# Category: OCaml

• ## Programming with Envelopes in OCaml and Haskell

In this post, I continue going through the famous paper “Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire” by Meijer et al.  They show that we can treat recursions as separate higher order functions known as recursion schemes.  Each of the four things in the paper title corresponds to a type of recursion scheme. …

• ## Zip and More in Haskell

In the last post we talked about using unfolds to zip and more in OCaml. In this post we write the equivalent functions in Haskell. Zip is in the standard library in Haskell. It’s actually so elegant that there isn’t much point using unfolds instead. To zip two lists, simply use the zip function: Prelude>…

• ## Using Unfolds to Zip and More in OCaml

This post picks up from where we left off here, where I explained anamorphisms.  In the last post we looked at iterating with anamorphisms.  Here we look at another example of applying unfolds: zip. Zip Zip may not be the most common example of anamorphisms but I want to cover it because it’s included in…

• ## Using Unfolds to Iterate in Haskell and OCaml

This post picks up from where we left off here, in which I explained anamorphisms.  Here we look at another example of applying unfolds: iterate.  Iterate Iterate is one of the most common uses of unfold.  The definition of the iterate function is: iterate f x = Cons (x, iterate f (f x)) E.g., let…

• ## Programming with Lenses in Haskell and OCaml

In this post, I continue going through the famous paper “Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire” by Meijer et al.  They show that we can treat recursions as separate higher order functions known as recursion schemes.  Each of the four things in the paper title corresponds to a type of recursion scheme. …

• ## Strings and Tries; Haskell Versus OCaml

While doing my OCaml MOOC exercise I came across a trie implementation for looking up words.  I find that the way OCaml treats strings is very different from the way Haskell does it.  It leads to different ways to implement the trie in the two languages. Strings and Tries in  Haskell Haskell is a pure…

• ## Eliminating Run Time Errors In OCaml and Haskell

Run Time Versus Compile Time Error Run time errors are those that happen when the program runs, as opposed to compile time errors which happen when the program compiles.  In a sense, having compile time errors is no big deal, because the errors guarantee that the ill-defined program won’t be running.  The programmer can fix…

• ## Folding Nonempty Lists in OCaml and Haskell

In the last post, I talked about catamorphisms in Haskell.  Specifically, the advantages of the foldr1 or foldl1 option in Haskell.  Namely, (1) not needing to specify the base case and (2) preserving polymorphisms in all applicable types.  In this post, I will show another way to fold nonempty list without using foldr1 or foldl1…

• ## Programming with Bananas in Haskell (Versus OCaml)

In the last post I talked about catamorphisms in OCaml.  In this post I compare that with Haskell.  We’ll see that Haskell gives you more options when implementing catamorphisms.  You don’t need to know Haskell to understand this post, I’ll introduce the required Haskell syntax along the way. Catamorphisms in Haskell As mentioned in the…

• ## Programming with Bananas in OCaml

By bananas, I mean banana brackets as in the famous paper “Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire” by Meijer et al.  In this post I only focus on bananas, also called catamorphisms. Recursion is core to functional programming.  Meijer et al. show that we can treat recursions as separate higher order functions…