;;;; Show the three different ways to deal with multiple return values (use-modules (example)) ;;; Multiple values as lists. By default, if more than one value is to ;;; be returned, a list of the values is created and returned. The ;;; procedure divide-l does so: (let* ((quotient/remainder (divide-l 37 5)) ;; divide-l returns a list of the two values, so get them: (quotient (car quotient/remainder)) (remainder (cadr quotient/remainder))) (display "37 divided by 5 is ") (display quotient) (display ", remainder ") (display remainder) (newline)) ;;; Multiple values as vectors. You can get vectors instead of lists ;;; if you want: (let* ((quotient-remainder-vector (divide-v 40 7)) ;; divide-v returns a vector of two values, so get them: (quotient (vector-ref quotient-remainder-vector 0)) (remainder (vector-ref quotient-remainder-vector 1))) (display "40 divided by 7 is ") (display quotient) (display ", remainder ") (display remainder) (newline)) ;;; Multiple values for multiple-value continuations. (The most ;;; elegant way.) You can get multiple values passed to the ;;; multiple-value continuation, as created by `call-with-values'. (call-with-values (lambda () ;; the "producer" procedure (divide-mv 91 13)) (lambda (quotient remainder) ;; the "consumer" procedure (display "91 divided by 13 is ") (display quotient) (display ", remainder ") (display remainder) (newline))) ;;; SRFI-8 has a very convenient macro for this construction: (use-modules (srfi srfi-8)) ;;; If your Guile is too old, you can define the receive macro yourself: ;;; ;;; (define-macro (receive vars vals . body) ;;; `(call-with-values (lambda () ,vals) ;;; (lambda ,vars ,@body))) (receive (quotient remainder) (divide-mv 111 19) ; the "producer" form ;; In the body, `quotient' and `remainder' are bound to the two ;; values. (display "111 divided by 19 is ") (display quotient) (display ", remainder ") (display remainder) (newline))