516036631c
git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@4141 626c5289-ae23-0410-ae9c-e8d60b6d4f22
66 lines
2 KiB
Scheme
66 lines
2 KiB
Scheme
;;;; Show the three different ways to deal with multiple return values
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(use-modules (example))
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;;; Multiple values as lists. By default, if more than one value is to
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;;; be returned, a list of the values is created and returned. The
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;;; procedure divide-l does so:
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(let* ((quotient/remainder (divide-l 37 5))
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;; divide-l returns a list of the two values, so get them:
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(quotient (car quotient/remainder))
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(remainder (cadr quotient/remainder)))
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(display "37 divided by 5 is ")
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(display quotient)
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(display ", remainder ")
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(display remainder)
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(newline))
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;;; Multiple values as vectors. You can get vectors instead of lists
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;;; if you want:
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(let* ((quotient-remainder-vector (divide-v 40 7))
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;; divide-v returns a vector of two values, so get them:
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(quotient (vector-ref quotient-remainder-vector 0))
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(remainder (vector-ref quotient-remainder-vector 1)))
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(display "40 divided by 7 is ")
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(display quotient)
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(display ", remainder ")
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(display remainder)
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(newline))
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;;; Multiple values for multiple-value continuations. (The most
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;;; elegant way.) You can get multiple values passed to the
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;;; multiple-value continuation, as created by `call-with-values'.
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(call-with-values (lambda ()
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;; the "producer" procedure
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(divide-mv 91 13))
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(lambda (quotient remainder)
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;; the "consumer" procedure
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(display "91 divided by 13 is ")
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(display quotient)
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(display ", remainder ")
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(display remainder)
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(newline)))
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;;; SRFI-8 has a very convenient macro for this construction:
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(use-modules (srfi srfi-8))
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;;; If your Guile is too old, you can define the receive macro yourself:
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;;;
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;;; (define-macro (receive vars vals . body)
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;;; `(call-with-values (lambda () ,vals)
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;;; (lambda ,vars ,@body)))
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(receive (quotient remainder)
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(divide-mv 111 19) ; the "producer" form
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;; In the body, `quotient' and `remainder' are bound to the two
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;; values.
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(display "111 divided by 19 is ")
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(display quotient)
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(display ", remainder ")
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(display remainder)
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(newline))
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