dst

Dst is a functional and imperative programming language and bytecode interpreter. It is a modern lisp, but lists are replaced by other data structures with better utility and performance (arrays, tables, structs, tuples). The language can also easily bridge to native code written in C, and supports abstract datatypes for interfacing with C. Also support meta programming with macros, and bytecode assembly for the dst abstract machine. The bytecode vm is a register based vm loosely inspired by the LuaJIT bytecode format, but simpler and safer (bytecode can be verified by the assembler).

There is a repl for trying out the language, as well as the ability to run script files. This client program is separate from the core runtime, so dst could be embedded into other programs.

Implemented in mostly standard C99, dst runs on Windows, Linux and macOS. The few features that are not standard C (dynamic library loading, compiler specific optimizations), are fairly straight forward. Dst can be easily ported to new platforms.

There is not much in the way of documentation yet because it is still a "personal project" and I don't want to freeze features prematurely. You can look in the examples directory, the test directory, or the file src/core/core.dst to get a sense of what dst code looks like.

For syntax highlighting, there is some preliminary vim syntax highlighting in dst.vim. Generic lisp syntax highlighting should, however, provide good results.

Features

• First class closures
• Garbage collection
• First class green threads (continuations)
• Mutable and immutable arrays (array/tuple)
• Mutable and immutable hashtables (table/struct)
• Mutable and immutable strings (buffer/string)
• Lisp Macros
• Byte code interpreter with an assembly interface, as well as bytecode verification
• Proper tail calls.
• Direct interop with C via abstract types and C functions
• Dynamically load C libraries
• Functional and imperative standard library
• Lexical scoping
• Imperative programming as well as functional
• REPL
• Interactive environment with detailed stack traces
• SQLite bindings

Documentation

API documentation and design documents can be found in the wiki. Not at all complete.

Usage

A repl is launched when the binary is invoked with no arguments. Pass the -h flag to display the usage information. Individual scripts can be run with ./dst myscript.dst

If you are looking to explore, you can print a list of all available macros, functions, and constants by entering the command (all-symbols) into the repl.

$ ./dst
Dst 0.0.0 alpha  Copyright (C) 2017-2018 Calvin Rose
dst:1:> (+ 1 2 3)
6
dst:2:> (print "Hello, World!")
Hello, World!
nil
dst:3:> (os.exit)
$ ./dst -h
usage: ./dst [options] scripts...
Options are:
  -h Show this help
  -v Print the version string
  -s Use raw stdin instead of getline like functionality
  -e Execute a string of dst
  -r Enter the repl after running all scripts
  -p Keep on executing if there is a top level error (persistent)
  -- Stop handling option
$

Compiling and Running

Dst only uses Make and batch files to compile on Posix and windows respectively. To configure dst, edit the header file src/include/dst/dst.h before compilation.

Posix

On most platforms, use Make to build dst. To

cd somewhere/my/projects/dst
make
make test

Windows

1. Install Visual Studio or Visual Studio Build Tools
2. Run a Visual Studio Command Prompt (cl.exe and link.exe need to be on the PATH) and cd to the directory with dst.
3. Run build_win to compile dst.
4. Run build_win test to make sure everything is working.

Examples

See the examples directory for some example dst code.

SQLite bindings

There are some sqlite3 bindings in the directory natives/sqlite3. They serve mostly as a proof of concept external c library. To use, first compile the module with Make.

make natives

Next, enter the repl and create a database and a table.

dst:1:> (import natives.sqlite3 :as sql)
nil
dst:2:> (def db (sql.open "test.db"))
<sqlite3.connection 0x5561A138C470>
dst:3:> (sql.eval db `CREATE TABLE customers(id INTEGER PRIMARY KEY, name TEXT);`)
@[]
dst:4:> (sql.eval db `INSERT INTO customers VALUES(:id, :name);` {:name "John" :id 12345})
@[]
dst:5:> (sql.eval db `SELECT * FROM customers;`)
@[{"id" 12345 "name" "John"}]

Finally, close the database connection when done with it.

dst:6:> (sql.close db)
nil