The context of this email is the proposal by Matthew Flatt that we move
to an easier-to-accept surface syntax for #lang racket2.
Matthew Flatt has heard more than enough from me of concern about this
proposal. But I should indicate that I'm highly sympathetic to the
goal. I would like to lay out the following observations:
- The challenge with s-expressions is largely in anxiety with something
that looks extremely alien. I suspect there's more fear from
instructors than students in encountering a lisp syntax; my
experience is that introducing someone who doesn't know differently
to a parenthetical syntax isn't scary for them, and they tend to like
it. But people who have *started out* with experience in a non-lispy
language tend to find it scary.
- Nonetheless, assumptions that various math operators should be infix
is understandable because that's what people see today.
- I am indeed very for growth in the community, though my main interest
in growth is in seeing a wider diversity of participants than just
raw numbers. Obviously other peoples' mileage may vary.
- We are at serious risk in this pivot of losing some key things:
- Many communities I have been in that have undertaken such a large
pivot to increase popularity expend enormous energy in the move to
the new thing, and in that process, the project actually collapses.
What I'm trying to say is that a pivot is a gamble; we should
calculate our odds carefully. (Indeed, the first thing I thought
when I heard that this might happen was, did I make a mistake in
shifting my work to Racket? It is unlikely I would have come to
Racket if there wasn't an equivalent amount of elegance.)
- I'm not sure if I could have understood Racket Week with a syntax
that didn't have the elegance of s-expressions. This is not to say
that *no* syntax can have that level of elegance where things can
be so clear, however.
IIRC Matthew's proposal for "#lang racket2" was something like the
following:
a) function(args ...) should work.
b) infix is necessary for math, such as 3 + 4
c) parentheses should be possible for grouping
The weird thing about the last one being that this is already kind of
true in s-expressions, but by ~default this also results in application.
Let me add one more suggested design goal:
- the new syntax should must not be significantly less elegant than
s-expressions.
Is there a way to achieve this? I actually think the best path forward
is to have a surface syntax that actually maps completely to
s-expressions, which is in fact universal that it can work with *any*
s-expression syntax.
I would suggest starting with Wisp as the basis for examining this:
https://dustycloud.org/blog/wisp-lisp-alternative/
https://srfi.schemers.org/srfi-119/srfi-119.html
Sweet-expressions may also be an alternative to explore. However, I
think Wisp is a more elegant base; it can transform *any* wisp code into
s-exp code. Not discussed in my blogpost about Wisp is that it also
supports infix via {3 + 4}. So ok, now we have that. And we can still
group:
{3 + {8 + 4}}
So that's points b) and c), but we don't have a) yet. Could we add it?
I think we can extend wisp with one thing and get everything we want: if
you have func(arg1 arg2 arg3) where the parenthesis comes *immediately*
after the symbol, that is rewritten to (func arg1 arg2 arg3). I will
call this version ~Wisp.
With all this, observe the following code rewritten from Scheme to ~Wisp:
(define (rgb-maker mk)
(lambda (sz)
(vc-append (colorize (mk sz) "red")
(colorize (mk sz) "green")
(colorize (mk sz) "blue"))))
define rgb-maker(mk)
lambda(sz)
vc-append(colorize(mk(sz) "red")
colorize(mk(sz) "green")
colorize(mk(sz) "blue"))
Here is another chunk of code, taken from HTdP2:
(and (or (= (string-length "hello world")
(string->number "11"))
(string=? "hello world" "good morning"))
(>= (+ (string-length "hello world") 60) 80))
To:
and(or({string-length("hello world") = string->number("11")}
string=?("hello world" "good morning"))
{{(string-length "hello world") + 60} >= 80})
And in fact the latter can transform itself *directly* into the former.
And the former technically is also still valid Wisp: you can embed
s-expressions into it and they still work.
I think this satisfies the requirements that Matthew laid out.
There's another major advantage of this. We can now write languages
that work either like:
#lang s-exp "mylang.rkt"
or:
#lang wisp "mylang.rkt"
The main thing that Wisp is missing right now is editor tooling so that
doing indentation is convenient. But that's more than feasible to add,
imo.
I think this is the best way to move forward without creating
significant divisions, throwing out valuable things we have, or making
future Racket Week courses all that much harder. What do people think?
- Chris
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