Is Haskell Declarative

Other Programming Languages

When it comes to programming languages, there are two main paradigms – imperative and declarative. Imperative languages focus on the steps and procedures needed to achieve a certain outcome, while declarative languages focus on expressing what the program should accomplish without specifying how it should be done. One language that is often heralded as a prime example of a declarative language is Haskell.

What is Haskell?

Haskell is a functional programming language that was designed to be purely functional and declarative. It was named after the mathematician Haskell Curry, and it has gained popularity among developers due to its strong type system, lazy evaluation, and elegant syntax.

As a functional programming language, Haskell emphasizes the use of functions as the main building blocks of a program. In Haskell, you define functions by specifying their input and output types and the pattern matching rules that define their behavior. These functions can then be composed and combined to create more complex programs. This approach allows for a high level of abstraction and modularity in Haskell programs.

Declarative Nature of Haskell

One of the key features that makes Haskell truly declarative is its focus on expressing computations in terms of mathematical functions. In Haskell, you do not need to explicitly state the steps or procedures to perform a computation. Instead, you define functions that describe the relationships between inputs and outputs.

For example, let’s say we want to calculate the square of a number in Haskell. Instead of writing code that explicitly calculates the square, we can define a function called “square” that takes a number as input and returns its square:

square :: Int -> Int
square x = x * x

By simply declaring the type signature and the pattern matching rule, we have defined a function that computes the square of a number. This declarative approach allows us to focus on what we want to achieve – calculating the square – without worrying about the specific steps involved.

Benefits of Declarative Programming

Declarative programming, as exemplified by Haskell, offers several advantages over imperative programming. One of the main benefits is increased readability and maintainability of code. Since declarative programs describe what needs to be done rather than how to do it, they are often more concise and easier to understand.

Another advantage of declarative programming is that it can lead to more efficient and optimized code. By expressing computations in a declarative manner, the compiler or interpreter has more freedom to optimize the execution. Haskell’s lazy evaluation, for example, allows for efficient and selective computation of values only when they are needed.


Haskell is undoubtedly a declarative programming language. Its focus on expressing computations in terms of mathematical functions allows developers to write clean, concise, and maintainable code. The declarative nature of Haskell also leads to improved efficiency and optimization of programs. Whether you are a fan of functional programming or just curious to explore new paradigms, Haskell is definitely a language worth diving into.