recv.scm of termite port to GNU Guile. NOTE: this may not be the best port, but it seems logical for the expanding of hygienic macro.

recv.scm

;; All hail the RECV form
(define-syntax-rule (recv . clauses)
  (let ((msg  (gensym "msg"))   ;; the current mailbox message
        (loop (gensym "loop"))) ;; the mailbox seeking loop
    
    ;; check the last clause to see if it's a timeout
    (let ((sesualc (reverse clauses)))
      (if (and (pair? (car sesualc))
               (eq? (caar sesualc) 'after))

          (let ((clauses1 (reverse (cdr sesualc)))
                ;; the code to compute the timeout
                (init (cadar sesualc))
                ;; the variable holding the timeout
                (timeout (gensym "timeout"))
                ;; the code to be executed on a timeout
                (on-timeout (cddar sesualc))
                ;; the timeout exception-handler to the whole match
                (e (gensym "e")))
            (primitive-eval
             (syntax->datum
              ;; RECV code when there is a timeout
              #`(let ((#,timeout #,init))
                  (with-exception-catcher
                   (lambda (#,e)
                     (if (mailbox-receive-timeout-exception? #,e)
                         (begin
                           (thread-mailbox-rewind)
                           #,@on-timeout)
                         (raise #,e)))
                   (lambda ()
                     (let #,loop ((#,msg (thread-mailbox-next #,timeout)))
                          (match/action
                           (thread-mailbox-extract-and-rewind)
                           (#,loop 
                            (thread-mailbox-next #,timeout))
                           #,msg
                           ;; extra clause to handle system events
                           (event 
                            (where (termite-exception? event))
                            (handle-exception-message event))
                           ;; the user clauses
                           #,@clauses1)))))))

          (primitive-eval
           (syntax->datum
            ;; RECV code when there is no timeout
            #`(let #,loop ((#,msg (thread-mailbox-next)))
                   (match/action
                    (thread-mailbox-extract-and-rewind)
                    (#,loop
                     (thread-mailbox-next))
                    #,msg
                    ;; extra clause to handle system events
                    (event 
                     (where (termite-exception? event))
                     (handle-exception-message event))
                    ;; the user clauses
                    #,@clauses))))))))