On Sun, Aug 25, 2013 at 10:54 PM, Stephen Chang <stch...@ccs.neu.edu> wrote: > Hi dev, > > I've noticed that Racket has a lot of convenient binding forms but > they don't fit together unless someone does it manually (for example > there's match-let and match-let-values, but no match-for). > > As an educational side project, I've been toying around with a > different way of organizing all the binding forms. What I wanted to do > is remove the need to manually combine current (and future) binding > forms by moving the binding "logic" to the binding site itself. > > Inspired by the in-vogue generics movement in the Racket world, I've > hacked together a sort of "generic interface" for bindings (in > reality, it's just a bunch of syntax properties right now), and > implemented alternate versions of some of the main binding forms that > support "instances" of these generic bindings. > > To illustrate, here are some test cases for a generic define I > implemented (~define). I also implemented binding "instances" for > match and values (which I arbitrarily named $ and ~v below) and I can > use these forms in (mostly) any binding position that supports generic > bindings. > > ;; functions >> (~define (f1 x y) (+ x y)) >> (f1 10 20) > 30 >> (~define (f2 ($ (list x y))) (+ x y)) >> (f2 (list 10 20)) > 30 > > ;; non-functions >> (~define a1 100) >> a1 > 100 >> (~define (~v a2 a3) (values 134 456)) >> a2 > 134 >> a3 > 456 > > You can nest bind instances too: > >> (~define (~v ($ (list b1 b2)) b3) (values (list 22 33) 44)) >> b1 > 22 >> b2 > 33 >> b3 > 44 > > Does anyone think this is useful? Or is it just a lot of work to save > a little bit of typing? Has anyone tried something like this before? > > It's still very much a work in progress but I figure I would ask for > some feedback earlier rather than too later, in case there is > something that makes this infeasible. > > Brave souls can look at the hackery here: > https://github.com/stchang/generic-bind/blob/master/generic-bind.rkt > (Warning: I'm still trying to figure out all the toys in the Racket > macro toolbox. For the most part, everything still looks like a > syntax-rule/case/parse/->datum nail to my hammer.) > > Technical question: I couldn't figure out a nice way to implement > ~let. Essentially, I want a let form where some clauses are let-values > and some are match-let, but I need to bind them all at the same time, > like let.
I'd introduce new names to bind them in sequence and then rename everything after it's all available. My letwreck does something similar: http://jeapostrophe.github.io/2013-08-05-letwreck-post.html#%28elem._%28chunk._~3cletwreck-defn~3e~3a1%29%29 > I can't define a ~lambda that works with values because > functions in racket can't receive values. Anyone have any ideas? > > Side observation: Trying to get things to work with multiple return > values was a pain because they don't compose (as in, functions can > produce them but can't receive them). Not sure if anything can be done > about this though. > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev -- Jay McCarthy <j...@cs.byu.edu> Assistant Professor / Brigham Young University http://faculty.cs.byu.edu/~jay "The glory of God is Intelligence" - D&C 93 _________________________ Racket Developers list: http://lists.racket-lang.org/dev