LunarML

A Standard ML compiler that produces Lua/JavaScript.

Building

You need a recent version of MLton to build the executable, and Lua 5.3+ or recent Node.js to run the compiled script.

$ make
$ make test
$ make test-stackless-handle
$ make test-luajit
$ make test-nodejs
$ make test-nodejs-cps
$ ./lunarml example/hello.sml
$ lua example/hello.lua
Hello world!

Usage

./lunarml [options] input.(sml|mlb)

Modes of operation:

• -mexe (default): Produces Lua/JavaScript program.
• -mlib: Produces a Lua module.

Targets:

• Lua
  • --lua (default): Targets Lua 5.3+.
  • --lua-stackless-handle: Targets Lua 5.3+. Allow deeply nested handle.
  • --luajit: Targets LuaJIT.
• JavaScript (ES2020+)
  • --js: Produces a JavaScript program.
  • --js-cps: Produces a JavaScript program (CPS mode; supports delimited continuations).

See --help for more information.

Features

• Most of SML '97 language, including signatures and functors
• A subset of SML Basis Library
• Interface to Lua
• Interface to JavaScript
• ML Basis system like MLton

Successor ML features:

• [x] Monomorphic non-exhaustive bindings
• [x] Simplified recursive value bindings
  • SML '97-compatible ordering for type variables is also supported: val <tyvarseq> rec <valbind>
• [x] Abstype as derived form
• [x] Fixed manifest type specifications
• [ ] Abolish sequenced type realizations
• [ ] Line comments
• [x] Extended literal syntax
  • [x] Underscores (e.g. 3.1415_9265, 0xffff_ffff)
  • [x] Binary notation (0b, 0wb)
  • [x] Eight hex digits in text (\Uxxxxxxxx)
• [ ] Record punning
• [x] Record extension
• [x] Record update
• [ ] Conjunctive patterns
• [ ] Disjunctive patterns
• [ ] Nested matches
• [ ] Pattern guards
• [ ] Optional bars and semicolons
• [ ] Optional else branch
• [ ] Do declarations
• [x] Withtype in signatures

Other extensions planned:

• [x] Vector expressions and patterns
• [ ] Packaged modules (like in Alice ML or HaMLet S)
• [x] Hexadecimal floating-point constants (e.g. 0x1p1024, 0x1.ffff_ffff_ffff_f)
• [x] Variably-encoded Unicode escape sequence in string literals (e.g. \u{3042})

The syntax of hexadecimal floating-point constants is:

<hexadecimal-integer-constant> ::= '~'? '0' 'w'? 'x' <hexadecimal-digit-sequence>
<hexadecimal-floating-point-constant> ::= '~'? '0x' <hexadecimal-digit-sequence> (<binary-exponent-part> | '.' <hexadecimal-digit-sequence> <binary-exponent-part>?)
<hexadecimal-digit-sequence> ::= <hexadecimal-digit> ('_'* <hexadecimal-digit>)*
<binary-exponent-part> ::= [pP] '~'? <digit> ('_'* <digit>)?

In short: the (binary) exponent part is optional and use tilde (~) for the negation symbol.

The \u{} escape sequence allows you to embed a Unicode scalar value in a string literal. The compiler encodes the character in UTF-(8|16|32), depending on the string type.