gistfile1.txt

(define-syntax (myapply stx)
  (define (is-underscore? x) (equal? '_ (syntax->datum x)))
  (syntax-case stx ()
    [(_ fun . args)
     (let* ([missing-ids (dar (filter is-underscore? (syntax->list #'args)))]
            [new-ids     (dar (take (length missing-ids) (generate-temporaries #'args)))]
            [new-args    (dar (replace-if is-underscore?  (syntax->list #'args) new-ids))])
       (with-syntax ([(new-arg ...) new-args]
                     [(new-id ...) new-ids])
         #'(lambda (new-id ...) (fun new-arg ...))))]))