oskar2517/microhaskell: Interpreter for a small subset of the Haskell programming language · GitHub

MicroHaskell

Lambda-calculus-based Interpreter for a Haskell subset

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MicroHaskell is an interpreter for a small subset of the Haskell programming language. It is designed around an intermediate representation rooted in the principles of the lambda calculus. This project serves both as a practical tool for experimenting with functional programming constructs and as an educational platform for studying the theoretical concepts of Haskell and functional languages more broadly.

• Lazy evaluation
• Untyped
• Bindings
• Function application
• Lambda expressions
• Lists (Church-encoded)
• Currying
• Recursive binding
• Basic arithmetic and conditionals
• Let bindings
• Custom operators and fixity declarations
• REPL with syntax highlighting

The following example demonstrates recursive bindings, arithmetic, currying, and higher-order functions in MicroHaskell:

-- Calculates the factorial of n
factorial n = if n == 0 then 1 else n * factorial (n - 1);

-- Calculates the n-th fibonacci number
fibonacci n =
    if n == 0 then 0
    else if n == 1 then 1
    else fibonacci (n - 1) + fibonacci (n - 2);

-- Calculates the great common divisor of a and b
gcd a b =
    if b == 0
    then abs a
    else gcd b (mod a b);

-- Partially applies gcd to 36 (currying)
curriedGcd = gcd 36;

constant = 42;

-- Applies op to arguments a and b
apply op a b = op a b;

-- Calculates whether five is an odd number. Uses let bindings.
isFiveOdd =
    let
        isOdd n =
            if n == 0 then 0
            else isEven (n - 1);

        isEven n =
            if n == 0 then 1
            else isOdd (n - 1);

        n = 5
    in
        isOdd n;

lambda = (\x y -> x * y) 3 4;

main = (apply (+) (curriedGcd 317523) (fibonacci 10)) * factorial 4 - constant + isFiveOdd * lambda;

For more examples, checkout the examples directory and the MicroHaskell prelude.

Potential future enhancements to MicroHaskell include:

• Pattern matching
• User-defined algebraic data types
• Improved error handling