Haskell vs Unison: What are the differences?

Introduction

Haskell and Unison are two programming languages that are both functional and statically typed. While they share some similarities, there are key differences between the two.

1. Evaluation Strategy: Haskell is based on a lazy evaluation strategy, also known as call-by-need, where expressions are only evaluated when their values are needed. In contrast, Unison uses a strict evaluation strategy, or call-by-value, where expressions are evaluated as soon as they are bound to variables.

2. Side Effects: Haskell strictly separates pure code from code that has side effects, such as I/O operations. It enforces immutability and provides a strong type system to ensure the absence of side effects in pure code. Unison, on the other hand, allows side effects to be performed anywhere, which can make it easier to write impure code but may lead to potential bugs and harder reasoning about the program's behavior.

3. Syntax and Expressiveness: Haskell has a more extensive syntax and richer type system compared to Unison. It supports a wide range of language features, such as type classes, higher-order functions, and type inference. Unison, on the other hand, has a simpler syntax and a less expressive type system, which can make it easier for beginners to learn.

4. Module System: Haskell has a hierarchical module system that allows code to be organized into modules and sub-modules. It provides visibility control and namespace management through imports and exports. Unison, on the other hand, has a content-based module system where modules are identified by their content hash. This enables a more flexible and decentralized module system compared to Haskell.

5. Naming Conventions: Haskell follows a snake_case naming convention, where words are separated by underscores. It also encourages the use of descriptive and self-explanatory names for variables and functions. Unison, on the other hand, follows a camelCase naming convention, where words are capitalized without underscores. It also allows the use of emojis as identifiers, which can make the code more expressive and fun to read.

6. Tooling and Community: Haskell has a mature and well-established ecosystem with a wide range of libraries, tools, and resources available. It has a large and active community that provides support and contributes to the development of the language. Unison, on the other hand, is a relatively new and evolving language with a smaller community and fewer libraries and tools available. However, it offers unique features like code synchronization and live coding, which can be appealing to certain use cases.

In summary, Haskell and Unison differ in their evaluation strategy, handling of side effects, syntax and expressiveness, module system, naming conventions, and the maturity of their tooling and community.