42 lines
1.6 KiB
Common Lisp
42 lines
1.6 KiB
Common Lisp
;;; Copyright 2013 Google Inc.
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;;;
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;;; Licensed under the Apache License, Version 2.0 (the "License");
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;;; you may not use this file except in compliance with the License.
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;;; You may obtain a copy of the License at
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;;;
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;;; http://www.apache.org/licenses/LICENSE-2.0
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;;;
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;;; Unless required by applicable law or agreed to in writing, software
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;;; distributed under the License is distributed on an "AS IS" BASIS,
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;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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;;; See the License for the specific language governing permissions and
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;;; limitations under the License.
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;;; In Lisp, it is possible for a function to return more than one value.
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;;; This is distinct from returning a list or structure of values.
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(define-test multiple-values
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(let ((x (floor 3/2))
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;; The macro MULTIPLE-VALUE-LIST returns a list of all values returned
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;; by a Lisp form.
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(y (multiple-value-list (floor 3/2))))
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(assert-equal x 1)
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(assert-equal y '(1 1/2)))
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(assert-equal '(24 3/4) (multiple-value-list (floor 99/4))))
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(defun next-fib (a b)
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;; The function VALUES allows returning multiple values.
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(values b (+ a b)))
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(define-test binding-and-setting-multiple-values
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;; The macro MULTIPLE-VALUE-BIND is like LET, except it binds the variables
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;; listed in its first argument to the values returned by the form that is its
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;; second argument.
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(multiple-value-bind (x y) (next-fib 3 5)
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(let ((result (* x y)))
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(assert-equal 40 result)))
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;; SETF can also set multiple values if a VALUES form is provided as a place.
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(let (x y)
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(setf (values x y) (next-fib 5 8))
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(assert-equal '(8 13) (list x y))))
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