smol-to-others

Translate SMoL programs to other programming languages:

• JavaScript
• Python
• (WIP) Racket
• (WIP) OCaml

Usage

racket main.rkt Examples/fact.smol

Design decisions

Sometimes, the most "natural" translation does not preserve the semantics. For example, (set! x 2) produces the void value in smol while x = 2 produces 2 in JavaScript. We decide to go for the natural translation because a goal of the whole smol project is to point out the consensus while acknowledging the differences.

TODO: Python non-local variables need to be declared. We also need to be careful about the distrinction between nonlocal and global.

The supported subset of SMoL

Know differences from the #lang smol

Immutable vectors are not supported. So ivec is not defined. pair is considered an alias of mpair.

pair? is not supported.

and, or, and not are not suported.

++ is not supported.

test/not is not supported.

spy is not supported.

let* and letrec are not supported.

zero? are not supported.

Lists are not supported. So cons, empty, list, map, filter, foldl, and foldr are not provided.

Some identifiers are not allowed to be used as variables. Specifically, the identifier must not be the same as one of the keywords and primitive operators. Furthermore, only alphabetic characters, numeric characters, -, _, *, !, and ? can appear in a variable. A variable must be non-empty and must not start with a number.

d ::= (defvar x e)
    | (deffun (f x ...) body)
e ::= c
    | x
    | (lambda (x ...) body)
    | (λ (x ...) body)
    | (let ([x e] ...) body)
    | (if e e e)
    | (begin e ... e)
    | (set! x e)
    | (pair e e)
    | (mpair e e)
    | (left e)
    | (right e)
    | (set-left! e e)
    | (set-right! e e)
    | (mvec e ...)
    | (vec-len e)
    | (vec-ref e e)
    | (vec-set! e e e)
    | (equal? e e)
    | (eq? e e)
    | (o e ...)
    | (e e ...)
o ::= < | <= | > | >=
    | + | - | * | /

body    ::= d ... e ... e
program ::= d ... e ...

Dependencies

• (for javascript) js-beautify
• (for python) autopep8