Lisp vs Haskell: how do they compare for functional programming projects?

Lisp lets a project mix functional, procedural, and object-oriented code in the same codebase, while Haskell locks in a purely functional, statically typed approach from the outset. Lisp dates to 1958, more than three decades before Haskell's 1990 release, and its multi-paradigm design reflects that earlier, more exploratory era of language design.

How do Lisp and Haskell compare on core design?

When does Lisp fit a functional programming project better?

Lisp fits projects where the team wants to extend the language itself through macros, mix functional code with procedural or object-oriented pieces as requirements shift, or develop interactively through a REPL rather than a strict compile cycle. It also fits naturally when a project already runs on a Lisp dialect such as Common Lisp or Scheme and needs to stay within that ecosystem.

When does Haskell fit better?

Haskell fits projects where correctness guarantees matter more than flexibility. Its type system catches mismatched types and unhandled cases at compile time rather than at runtime, and its lazy evaluation and algebraic data types map cleanly onto problems like parsers, compilers, and rule-based financial or scientific logic. Teams that want functional purity enforced by the compiler, not just encouraged by convention, lean toward Haskell.

Who should choose which?

Teams that value exploratory, macro-driven development spanning multiple paradigms tend to pick Lisp. Teams that need a compiler to enforce functional discipline and catch type errors before code ever runs tend to pick Haskell. Neither choice is really about functional programming in the abstract; it comes down to how much structure a team wants imposed on it before code ships.