Sugar – a typed lispy language targeting webasm/wat

Compiler is incomplete but I have written some reasonably complex programs.

Interesting to read for the, very short, compiler.

Thanks for reading the post :)

Update 2020-12-07: There was a bug in the macro expansion logic. I've backported the fix to the linked source and explained the bug in the 'mistakes' section.

In the Coursera course Programming Languages, I ported some of the first assignments from SML to F# and Typed Racket, and you can see the similarities of type annotations in the very simple examples below.

SML:

    (* Helper function. Takes a generic list and an integer n and returns the nth element of the list. *)
    fun get_nth_element (xs : 'a list, n : int) =
        if n = 1
        then hd xs
        else get_nth_element(tl xs, n-1)

    (* Takes a list of strings and an integer n and returns the nth element of the list. *)
    fun get_nth (strings : string list, n : int) =  get_nth_element(strings,n)

    /// Helper function. Takes a generic list and an integer n and returns the nth element of the list.
    let rec getNthElement (xs : 'a list, n : int) =
        if n = 1
        then List.head xs
        else getNthElement(List.tail xs, n-1)

    /// Takes a list of strings and an integer n and returns the nth element of the list.
    let getNth (strings : string list, n : int) =  getNthElement(strings,n)

    #lang typed/racket

    ;; Helper function. Takes a generic list and an integer n and returns the nth element of the list.
    (: get-nth-element (All (T) (Listof T) Integer -> T))
    (define (get-nth-element xs n)
      (if (equal? n 1)
          (first xs)
          (get-nth-element (rest xs) (- n 1))))

    ;; Takes a list of strings and an integer n and returns the nth element of the list.
    (: get-nth ((Listof String) Integer -> String))
    (define (get-nth strings n) (get-nth-element strings n))