What is a string in OCaml?

Strings. A string s of length n is an indexable and immutable sequence of n bytes. For historical reasons these bytes are referred to as characters. The semantics of string functions is defined in terms of indices and positions.

What does -> mean in OCaml?

The way -> is defined, a function always takes one argument and returns only one element. A function with multiple parameters can be translated into a sequence of unary functions.

What does H :: t mean in OCaml?

The pattern h :: t matches any non-empty list, calls the head of the list h (one element, the first one), and the tail of the list t (zero or more elements after the first one). The operator :: is the list constructor (often called “cons”), which is why these patterns match lists.

What is ref in OCaml?

ref’s (references) allow you to make any type of value mutable (sort of). More properly, ref’s are an abstraction of the concept of an “updateable location” which can be initialized to any value: like a memory cell.

How do I compare strings in OCaml?

You can compare strings with the usal comparison operators: = , <> , < , <= , > , >= . You can also use the compare function, which returns -1 if the first string is less than the second, 1 if the first string is greater than the second, and 0 if they are equal.

Is OCaml similar to Haskell?

Libraries and ecosystem If Haskell is a niche language, then OCaml is a super-niche language. The OCaml community is much smaller. Where Haskell is doing more-or-less fine with libraries, OCaml has significantly less to propose. There are some nice libraries in OCaml, but in many areas the situation is not perfect.

What is () in OCaml?

This is a way to indicate there is no value for an argument. It’s necessary to do this in ML because all functions are unary. You can’t have a function with zero arguments, so instead you pass an argument containing no information, which is () . Follow this answer to receive notifications.

Is OCaml immutable?

In OCaml, records are immutable by default, but individual fields are mutable when marked as such.

Is OCaml imperative?

While OCaml is a functional programming language and emphasises pure functional style, it allows mutable (variables and values) and hence imperative programming style.

What is == in OCaml?

OCaml distinguishes between structural equality and physical equality (essentially equality of the address of an object). = is structural equality and == is physical equality.

What does |> do in OCaml?

The |> operator represents reverse function application. It sounds complicated but it just means you can put the function (and maybe a few extra parameters) after the value you want to apply it to.

What are Functors in OCaml?

A functor is a module that is parametrized by another module, just like a function is a value which is parametrized by other values, the arguments. It allows one to parametrize a type by a value, which is not possible directly in OCaml without functors.

Why is OCaml not popular?

The only problem with OCaml is that not many people know how to code in it, and therefore not many people use it.

Is Haskell harder than OCaml?

In fact I’ve generally found OCaml to be substantially worse at type inference than Haskell, requiring frequent type annotations and cluttering up the code. Haskell’s learning curve is steeper, but it is simpler in some ways, especially once you’re familiar. I think where ReasonML/OCaml wins hands-down is its compiler.

How to pattern match a list in OCaml?

We can be more specific about the structure of elements inside a list, and OCaml will infer the correct function type: By combining these patterns together, we can process any arbitrarily complex list. The keyword function can be used to initiate pattern-matching on the the last argument of a function.

What is the difference between always-matching _ and tuple in OCaml?

There are two ways this matters: the memory layout differs between the two (a tuple is an extra indirection), and the ability to create or match using a tuple: Note, however, that OCaml allows us to use the always-matching _ in either version:

What are compound data types in OCaml?

We have already seen simple data types such as int, float, string, and bool. Let’s recap the built-in compound data types we can use in OCaml to combine such values. First, we have lists which are ordered collections of any number of elements of like type: Next, we have tuples, which collect a fixed number of elements together:

What is pattern matching in functional programming languages?

Functional language’s Pattern Matching is the same idea, but applied to any expressions of the language, typically list-like data.