(define-syntax (define-command stx)
  (syntax-case stx (optional)
    [(_ com (pl (a b) ... optional (oa ob)) props body ...)
     #`(define (com pl . args)
        (cond
           [(< (length args) #,(length (syntax->datum #'(a ...))))
            (sendmsg #,(string-append "Not enough arguments for " (string-upcase (symbol->string (syntax-e #'com))) ".") pl)]
           [else
            (let/cc hop (let #,(letrec ((P (λ (ca cb n) (if (null? ca)
                                                           #`((ob (#,(syntax-e #'oa) (list-ref? args #,n) pl hop)))
                                                           #`((#,(car cb) (#,(car ca) (list-ref args #,n) pl hop)) #,@(P (cdr ca) (cdr cb) (+ n 1)))))))
                                  (P (syntax-e #'(a ...)) (syntax-e #'(b ...)) 0)) #,(if (syntax-e #'props) #`(act (λ () body ...) pl props ob) #`(begin body ...))))]


         ))]
    [(_ com (pl (a b) ... . m) props body ...)
     #`(define (com pl . args)
         (if (< (length args) #,(+ (length (syntax->datum #'(a ...))) (if (null? (syntax-e #'m)) 0 1)))
             (sendmsg #,(string-append "Not enough arguments for " (string-upcase (symbol->string (syntax-e #'com))) ".") pl)
             (let/cc hop (let #,(letrec ((P (λ (a b n) (if (null? a)
                                                           (if (null? (syntax-e #'m)) #`() #`((m (string-join (list-tail args #,n)))))
                                                           #`((#,(car b) (#,(car a) (list-ref args #,n) pl hop)) #,@(P (cdr a) (cdr b) (+ n 1)))))))
                                  (P (syntax-e #'(a ...)) (syntax-e #'(b ...)) 0)) #,(if (syntax-e #'props) #`(act (λ () body ...) pl props args) #`(begin body ...))))))]

    ))