diff --git a/README.md b/README.md index 1dc4b04..35288a7 100644 --- a/README.md +++ b/README.md @@ -13,7 +13,38 @@ AlexScript (which is a misnomer; the language will soon be renamed since it's not actually a scripting language) is a programming language designed to have a functional feel and very high-level ergonomics while maintaining speed using strictly-controlled, -deterministic memory management. +deterministic memory management. The language is capable of compiling +to C (and possibly other languages in the future), allowing for +maximum portability without having to write a new backend for the +compiler for every possible target; also, the compiler and tooling +will eventually be rewritten in AlexScript to allow for maximum +portability. + +## Example + +``` +// Calculates the nth fibonacci number. +def fibonacci (0: U32) : U32 = 0 + | fibonacci 1 = 1 + | fibonacci n = fibonacci (n - 2) + fibonacci (n - 1); + +// Prompts the user for a number n, and prints the Fibonacci numbers up +// to n. +def fibPrompt + = do { + print "Enter a number: "; + num <- read <$> getLine; + sequence_ (print . fibonacci <$> [0 .. num]); + }; + +// Program entry point. +def main: IO () + = fibPrompt; +``` + +Note that type annotations are always optional; here they're given for +`fibonacci` and `main` for illustrative purposes, but omitted for +`fibPrompt` (for which the compiler infers the return type `IO ()`). ## Tools @@ -71,6 +102,24 @@ Some features the language will most likely have: can be converted to an `IO` computation using `UNSAFE_assertMemorySafe : MemoryUnsafe a -> IO a`. - Further safety monads may be added in the future. -- +- The language achieves good performance by guaranteeing a number of + optimizations: + - Since the language uses a linear type system, garbage collection + is not done; instead, values are stored on the stack unless + explicitly declared to be on the heap, and heap-stored values are + cleaned up at deterministic points as calculated at compile time. + - Functions of type `Fn t -> t` are optimized into functions that + operate on pointers to `t`, i.e., notionally, `Fn (*mut t) -> ()`, + where `*mut t` is a mutable pointer to a type `t`. + - Types that contain an optional, non-null pointer like `Option (Box + a)`, `Option (Ref a)`, etc., are optimized into nullable pointers. + - Since the language has no loops, the compiler guarantees + optimization of tail-call recursion to loops on all functions, as + is standard in functional languages. ## Compilation + +When invoked with no flags, AlexScript by default compiles source code +directly to code that is valid C and C++, then calls the system C +compiler to generate an object file, then calls the system linker to +generate an executable file.