Carp/README.md

Carp

Carp is a small programming language designed to work well for interactive and performance sensitive use cases like games, sound synthesis and visualizations.

The key features of Carp are the following:

• Automatic and deterministic memory management (no garbage collector or VM)
• Inferred static types for great speed and reliability
• Live reloading of code, REPL-driven development, aka "fun"
• Ownership tracking enables a functional programming style while still using mutation for fast updating of data structures
• No hidden performance penalties – allocation and copying is explicit
• Very good integration with exisiting C code

The Language

Carp borrows its looks from Clojure but the runtime semantics are much closer to those of ML or Rust. Here's a sample program:

(defn fib (n)
  (if (< n 2)
    1
    (+ (fib (- n 2)) (fib (- n 1)))))

This compiles to the equivalent of the following C program:

int fib(int n) {
  if(n < 2) {
    return 1;
  } else {
    return fib(n - 2) + fib(n - 1);
  }
}

The most important thing in Carp is to work with arrays of data. Here's how that looks:

(defn move-enemies (enemies)
  (map (fn (enemy) 
         (let [moved (move enemy)]
           (if (< (.x moved) 0.0f) 
               (restart moved) 
               moved)))
       enemies))

The ownership system can see that the map function takes over the enemies-array. This allows 'map' to use C-style mutation of the array and return the same data structure back afterwards, no allocation or deallocation needed!

The Compiler

Carp is very tightly integrated with it's compiler which itself is written in a dynamic version of Carp (which in turn is implemented in C). To work on a Carp program you run carp which starts the REPL. Everything you want to do to your program can be controlled from here.

For example, to compile the function defined above you would enter the following:

λ> (bake fib)

This results in the compiler analyzing the code form for 'fib' and compiling it to some very fast binary code, immediately loading this back into the REPL so that it can be called from there.

(C) Erik Svedäng 2015 - 2016