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README.md
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README.md
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Please keep this document correctly word-wrapped at 70 columns and
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with no trailing whitespace or blank lines at the end! Merge requests
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with modifications to this document will be not be accepted until it
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is formatted correctly! ~~abb
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-->
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# Drim
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Drim is a programming language designed to have the very high-level
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ergonomics and provable correctness of a purely functional language,
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while maintaining speed using strictly-controlled, deterministic
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memory management. The language is capable of compiling to C (and
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possibly other languages in the future), allowing for maximum
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portability without having to write a new backend for the compiler for
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every possible target; also, the compiler and tooling will eventually
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be rewritten in Drim to allow for maximum portability.
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Syntactically, the language primarily resembles a mixture between
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standard ML and Rust; the language always ignores whitespace.
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Drim is licensed under the GNU General Public License, version 3 or
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later. See the `LICENSE` file for details.
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## Example
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```
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// Calculates the nth fibonacci number.
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def fibonacci (n: U32) : U32 = match n {
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0 => 0,
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1 => 1,
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n => fibonacci (n - 2) + fibonacci (n - 1),
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};
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// Prompts the user for a number n, and prints the Fibonacci numbers up
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// to n.
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def fibPrompt = do {
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print "Enter a number: ";
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num <- read <$> getLine;
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sequence_ (print . fibonacci <$> (0 .. num));
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};
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// Program entry point.
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def main : IO ()
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= fibPrompt;
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```
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Note that type annotations are always optional; here they're given for
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`fibonacci` and `main` for illustrative purposes, but omitted for
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`fibPrompt` (for which the compiler infers the return type `IO ()`).
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## Tools
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This repository contains the following tools:
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- `drimc-rs`, the Stage-1 Drim compiler, written in Rust. This can be
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used as a binary with a fairly standard compiler CLI, or as a
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library for use in other Rust programs.
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The following tools do not exist yet, but are planned:
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- `drimc`, the main Drim compiler written in Drim. This program
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supports a superset of the behavior of `drimc-rs`, and exposes a
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library that can be used by other Drim programs in addition to a the
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compiler CLI.
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- `drim`, the interactive Drim interpreter, a wrapper around `drimc`.
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- `drimd`, the Language Server Protocol (LSP) server for Drim code
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support in editors, supporting definition peeking and lookup,
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renaming variables and modules, etc.
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- `drimfmt`, the standard formatter for Drim code; all Drim code used
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in this repository must be formatted with `drimfmt`, and its use is
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recommended for other projects.
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- `drimdoc`, the documentation generator.
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- `drim-mode`, an Emacs mode for editing Drim code, supporting syntax
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highlighting, automatic indentation, some basic keybindings for
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common tasks, Emacs-side LSP integration for communicating with
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`drimd`, and a collection of `yasnippet` snippets for inserting
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common Drim constructs.
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- `drim-vsc`, Visual Studio Code plugins and tools for editing
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AlexScript code.
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- `drim-vim`, tools and configuration files for optimizing Vim
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and Neovim for editing Drim code.
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## Language features
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The language is mostly influenced by Rust and Haskell: it has strict
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safety requirements and borrow-checked memory management like that of
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Rust, but its syntax and type system are similar to those of Haskell.
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Some features the language will most likely have:
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- All functions are pure by default; side effects are chained together
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using an `IO` monad.
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- Despite the language's purity, expressions will be strictly
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evaluated to provide more programmer control.
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- Different monads represent different levels of safety, and can be
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converted using functions marked as `UNSAFE`. The intention is that
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code can be audited by manually checking that all the `UNSAFE`
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transformations are sound, and code that contains no `UNSAFE`
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function calls are guaranteed to satisfy varying definitions of
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soundness:
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- The `IO` monad represents computations that might have side
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effects on the real world. If a computation of type `IO` is known
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by the programmer to not have side effects on the real world, then
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it can be converted to a pure computation using the standard
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library function `UNSAFE_assertPure : IO a -> a`.
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- The `MemoryUnsafe` monad represents computations that might read
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from or write to memory that is not allocated correctly: for
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example, `readPtr`, which reads from a raw pointer, is of type
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`MemoryUnsafe a` because the pointer is not known to be valid. If
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a computation has been confirmed to be safe by the programmer, it
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can be converted to an `IO` computation using
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`UNSAFE_assertMemorySafe : MemoryUnsafe a -> IO a`.
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- Further safety monads may be added in the future.
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- The language achieves good performance by guaranteeing a number of
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optimizations:
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- Since the language uses a linear type system, garbage collection
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is not done; instead, values are stored on the stack unless
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explicitly declared to be on the heap, and heap-stored values are
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cleaned up at deterministic points as calculated at compile time.
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- Functions of type `Fn t -> t` are optimized into functions that
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operate on pointers to `t`, i.e., notionally, `Fn (*mut t) -> ()`,
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where `*mut t` is a mutable pointer to a type `t`.
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- Types that contain an optional, non-null pointer like `Option (Box
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a)`, `Option (Ref a)`, etc., are optimized into nullable pointers.
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- Since the language has no loops, the compiler guarantees
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optimization of tail-call recursion to loops on all functions, as
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is standard in functional languages.
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## Compilation
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When invoked with no flags, Drim by default compiles source code
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directly to code that is valid C and C++, then calls the system C
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compiler to generate an object file, then calls the system linker to
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generate an executable file.
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Drim is now hosted at [[https://codeberg.org/gkgoat/drim]].
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