>     The point of keyword args is to be optional
>
> Sometimes they are all in fact mandatory, but there are too many and we
> want to use keywords for their self-documenting powers.  In Harlan, my
> favorite toy language (don't bother googling for it),

The GPU thing? https://github.com/eholk/harlan

> all procedures are
> called using keywords unless they have less than three arguments.  If
> the arguments are left and right, the name is a binary operator, and if
> there is only right, a unary operator.

Smalltalk does that as well. And IIRC Swift and Objective-C who got it
from Smalltalk.

Racket can do required keyword arguments. If Scheme gets an "all bells
and whistles" keyword SRFI, maybe that SRFI should let people make them.