Introduction

Lambda Zero is a minimalist pure lazy functional programming language with:

• All the standard Lambda Calculus features (first class functions, closures, currying, recursion, nested function definitions, ...)
• Lazy evaluation (infinite data structures, increased modularity, ...)
• Algebraic data types (enumerations, tuples, lists, trees, records/structs, maybe/optional types, either types, monads, ...)
• Pattern matching (case expressions, tuple destructuring, ...)
• Automatic garbage collection
• Semantic whitespace
• Unicode support (UTF8)
• User-defined lexically-scoped operator syntax and semantics
• Hindley-Milner static type inference (implemented in Lambda Zero)
• A self-interpreter

And the interpreter is less than 2500 lines of C code.

Sample Code

Hello World

main(input) ≔ "hello world"

Factorial

n ! ≔ n ⦊ case 0 ↦ 1; case ↑ n′ ↦ n ⋅ n′ !

Quicksort

sort ≔ case [] ↦ []; case n ∷ ns ↦ sort(ns ¦ (≤ n)) ⧺ [n] ⧺ sort(ns ¦ (> n))

Infinite list of natural numbers

iterate(f, x) ≔ x ∷ iterate(f, f(x))
(…) ≔ iterate(↑)
naturals ≔ 0 …

Infinite list of Fibonacci numbers

fibonaccis ≔ f(0, 1) where f(m, n) ≔ m ∷ f(n, m + n)

Infinite list of prime numbers

primes ≔ p(2 …) where p ≔ case [] ↦ []; case n ∷ ns ↦ n ∷ p(ns ¦ (% n ≠ 0))

Building

Make sure a C compiler is installed and run the make script in the bootstrap-interpreter directory:

cd bootstrap-interpreter
./make

Running

From the bootstrap-interpreter directory:

./run SOURCEFILE

For example, try this sample program that prints out an infinite list of prime numbers:

./run test/samples/primes.zero

The run script prepends the prelude to the SOURCEFILE and passes the result to main.

Stability

Breaking changes may be made at any time.