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From: Chris Marusich <cmmarusich@gmail.com>
To: guile-user@gnu.org
Subject: Multiple values passed as single argument to procedure
Date: Sun, 11 Jun 2017 00:56:23 -0700	[thread overview]
Message-ID: <87mv9fnejc.fsf@gmail.com> (raw)

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Hi,

I've noticed that when one passes multiple values as a single argument
to a procedure, only the first value gets used.  Is this expected?
Here's an example:

--8<---------------cut here---------------start------------->8---
$ guile
GNU Guile 2.2.2
Copyright (C) 1995-2017 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (define (proc x) x)
scheme@(guile-user)> (proc (values 1 2))
$1 = 1
scheme@(guile-user)> 
--8<---------------cut here---------------end--------------->8---

I've looked in a few places to try to figure out the answer to this
question, but I haven't found much.  In addition to the guile-devel and
guile-user email list archives, I've checked the following sections in
the manual:

(guile) Binding Multiple Values
(guile) Lambda
(guile) Fly Evaluation
(guile) Compiled Procedures
(guile) Expression Syntax

However, I did find the following information in R6RS (Section 5.8:
"Multiple return values"), which seems possibly relevant:

"Not all continuations accept any number of values. For example, a
continuation that accepts the argument to a procedure call is guaranteed
to accept exactly one value.  The effect of passing some other number of
values to such a continuation is unspecified."

-- 
Chris

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             reply	other threads:[~2017-06-11  7:56 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-11  7:56 Chris Marusich [this message]
2017-06-11  8:28 ` Multiple values passed as single argument to procedure David Kastrup
2017-06-11 20:36 ` Mark H Weaver
2017-06-11 21:31   ` Mark H Weaver
2017-06-12  0:19   ` Chris Marusich
2017-06-12  4:25     ` Mark H Weaver
2017-06-12  8:19       ` Chris Marusich
2017-06-12  8:55         ` Neil Jerram
2017-06-12  9:48           ` Neil Jerram
2017-06-12  9:39         ` David Kastrup
2017-06-12 11:31           ` Mark H Weaver
2017-06-12 14:24             ` David Kastrup
2017-06-13  2:26               ` Mark H Weaver
2017-06-13  3:09                 ` Mark H Weaver
2017-06-13  3:45                 ` Mark H Weaver
2017-06-13 11:17                 ` dsmich
2017-06-26 11:25                   ` Alex Vong
  -- strict thread matches above, loose matches on Subject: below --
2017-09-01 19:39 Chris Marusich

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