[racket] Sweet expressions; or making it easier to introduce Racket to me and my coworkers :-)

On 7/20/11 3:19 PM, Asumu Takikawa wrote:
> On 2011-07-17 19:13:07 +0200, Danny Wilson wrote:
>> Hi List,
>>
>> Short version: is there an implementation of
>> http://www.dwheeler.com/readable/sweet-expressions.html  for
>> typed/racket or just racket?
>
> I've been curious about sweet expressions myself for a while
> too, so I went ahead and ported David Wheeler's
> implementation for Racket and made it a language you can use
> from planet.
>
> To use, write a #lang line like this:
>
>    #lang asumu/sweet racket
>
>    printf("Hello")

Cute!  Thanks for the cool planet package.  Here's a slightly larger 
example using Redex, adapted from redex/examples/arithmetic.rkt:

#lang planet asumu/sweet racket
require rename-in(redex [term quote])

define-language lang
   e n
     δ1(e)
     δ2(e e)
   δ1 √ add1 sub1
   δ2 + - * /
   E hole
     δ1(E)
     δ2(e E)
     δ2(E e)
   n number

define v
   reduction-relation lang
     { √(n) --> ,sqrt('n) }
     { add1(n) --> ,add1('n) }
     { sub1(n) --> ,sub1('n) }
     { +(n_1 n_2) --> ,+('n_1 'n_2) }
     { -(n_1 n_2) --> ,-('n_1 'n_2) }
     { *(n_1 n_2) --> ,*('n_1 'n_2) }
     { /(n_1 n_2) --> ,/('n_1 'n_2) }

define -->_v
   context-closure v lang E

traces -->_v '-(*(√(36) /(1 2)) +(1 2))

As a thank you, I opened two tickets on planet. ;)

David