BLisp: A Statically Typed Lisp Like Language

Post by dharmaturtle » Mon, Jun 28, 2021, 1:08 PM UTC

michaelsbradley wrote: post #21

valenterry wrote: post #3

I always feel that for lisp-like languages it's just not a good idea to make them statically typed. Their power is derived from macros and the fact that code is data and the other way around. For statically typed languages, they only feel ergonomic to me if they have highly specialized syntax and if they really leverage the type-system (which is often in conflict with macros and runtime flexibility).

Nim is statically typed and has a powerful macro facility: https://nim-lang.org/docs/manual.html#macros https://nim-lang.org/docs/macros.html

Post by mumblemumble » Mon, Jun 28, 2021, 2:37 PM UTC

valenterry wrote: post #39

tines wrote: post #37

Earlier quoted context omitted.

No problem. I'm interested to hear though why you think unrestricted macros make the type system unsound. Can you explain? The code generated by macros would be type-checked in the scheme I described, and type-unsafe code can't be executed by the macro itself, so it seems safe to me.

That is more of my impression that I have gathered from watching programming languages evolving. Rust is a good example, where they tried hard and the macros still become unsound. Scala is another good example where macros where unsound first and they had a really hard time to make them sound and work with the type-system - they lost a lot of power in the process. Now, that doesn't have to mean that there is some inh…

Post by hajile » Mon, Jun 28, 2021, 7:01 PM UTC

moonchild wrote: post #26

Is this a lisp? It looks like an ml with s-expressions.

Post by kazinator » Tue, Jun 29, 2021, 12:34 AM UTC

weavie wrote: post #35

simiones wrote: post #28

Earlier quoted context omitted.

Just for completeness, the correct macro would look like this: (defmacro double (x) (let ((temp (gensym)) `(let ((,temp ,x)) (+ temp temp)))) This way, when you write (double (parse-integer (read-line)) it would expand to (let ((#:uniqueName123 (parse-integer (read-line))) (+ #:uniqueName123 #:unique_symbol_123)) This guarantees that that the macro will not accidentally refer to some outside variable, and that it's a…

Surely (defmacro double (x) (let ((temp (gensym)) `(let ((,temp ,x)) (+ ,temp ,temp))))

   (declaim (inline double))

   (defun double (x) (+ x x))

Post by simiones » Tue, Jun 29, 2021, 10:18 AM UTC

exdsq wrote: post #44

simiones wrote: post #36

Earlier quoted context omitted.

Oops, yes...

And this thread is why types help :)

  (compile nil '(lambda (x) (double x)))
  ;Compiler warnings :
  ;   In an anonymous lambda form: Undeclared free variable TEMP
  ;   In an anonymous lambda form: Unused lexical variable #:G520

  (let ((temp 100))
    (double 10))
  ;returns 200

  (declaim (special temp))
  (compile 'nil (lambda (x) (double x))
  ;Compiler warnings :
  ;   In an anonymous lambda form: Unused lexical variable #:G524