keyvals.rkt

#lang racket

(require syntax/parse/define
         (for-syntax syntax/parse))

(begin-for-syntax
  (writeln "Now Compiling"))
(writeln "Now Running")

(define-syntax (caps stx)
  (raise-syntax-error 'caps "Can't use here"))
(define-syntax (happy stx)
  (raise-syntax-error 'happy "Can't use here"))

(begin-for-syntax
  (define-syntax-class options
    #:literals (caps happy)
    (pattern ((~or (~optional (~and caps cps))
                   (~optional (~and happy hpy))) ...))))

(define-syntax-parser hi
  [(_ opts:options name)
   (define hi (if (attribute opts.cps) "HI" "hi"))
   (define end (if (attribute opts.hpy) ", I'm happy" ""))
   #`(format "~a ~a~a" #,hi name #,end)])

(hi (caps)
    "Leif")

KeywordArgs.rkt

#lang racket

(require syntax/parse/define
         (for-syntax syntax/parse))

(begin-for-syntax
  (writeln "Now Compiling"))
(writeln "Now Running")

(define-syntax-parser hi
  [(_ ((~or (~optional (~and #:caps caps))
            (~optional (~and #:happy happy))) ...)
      name)
   (define hi (if (attribute caps) "HI" "hi"))
   (define end (if (attribute happy) ", I'm happy" ""))
   #`(format "~a ~a~a" #,hi name #,end)])

(hi (#:caps #:happy)
    "Leif")