Haskell vs. JavaScript vs. Nix vs. PureScript Comparison Chart

Every expression in Haskell has a type that is determined at compile time. All the types composed together by function application have to match up. If they don't, the program will be rejected by the compiler. Types become not only a form of guarantee, but a language for expressing the construction of programs. Every function in Haskell is a function in the mathematical sense (i.e., "pure"). Even side-effecting IO operations are but a description of what to do, produced by pure code. There are no statements or instructions, only expressions that cannot mutate variables (local or global) nor access state like time or random numbers. You don't have to explicitly write out every type in a Haskell program. Types will be inferred by unifying every type bidirectionally. However, you can write out types if you choose, or ask the compiler to write them for you for handy documentation.

Nix is a tool that takes a unique approach to package management and system configuration. Learn how to make reproducible, declarative, and reliable systems. Nix builds packages in isolation from each other. This ensures that they are reproducible and don't have undeclared dependencies, so if a package works on one machine, it will also work on another. Nix makes it trivial to share development and build environments for your projects, regardless of what programming languages and tools you’re using. Nix ensures that installing or upgrading one package cannot break other packages. It allows you to roll back to previous versions and ensures that no package is in an inconsistent state during an upgrade. Nix is a purely functional package manager. This means that it treats packages like values in purely functional programming languages such as Haskell, they are built by functions that don’t have side effects, and they never change after they have been built.