[r6rs-discuss] [Formal] Clarify the description of which continuations take multiple values

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Submitter: Alan Watson
Email address: alan_at_alan-watson.org
Issue type: Clarification
Priority: Minor
Component: Base Library
Version: 5.91
Summary: Clarify the description of which continuations take multiple 
values.
The number of values accepted by certain continuations is touched upon
in 4.5 and then defined more precisely in 9.5.7 and 9.18 in the
descriptions of the let-values and let*-values syntac and the values and
call-with-values procedures.
Section 4.5
===========
When I first read 4.5, I was confused by its vagueness, because I
thought it would be the definitive description the number of values
accepted by certain continuations and the behaviour when an unexpected
number of values is supplied. However, on repeated reading, it became
clear that it is simply introducing concepts which are firmed up later
in 9.18.
I would changing the second paragraph of 4.5 as follows (my additions
in upper case):
   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 ... then
   an exception is raised. A MORE COMPLETE DESCRIPTION OF THE NUMBER OF
   VALUES ACCEPTED BY DIFFERENT CONTINUATIONS AND THE CONSEQUENCES OF
   PASSING AN UNEXPECTED NUMBER OF VALUES IS GIVEN IN THE DESCRIPTION OF
   THE VALUES PROCEDURE IN SECTION 9.18.
Section 9.5.7
=============
The description of let-values currently says "If no formals match, ...".
Would it not be better to say "If the formals do not match ..."?
Section 9.18
============
Mention let-values and let*-values. That is, change the second paragraph
to (my changes in upper case):
   Except for these and the continuations created by call-with-values,
   LET-VALUES, AND LET*-VALUES, all other continuations take exactly one
   value. The effect of passing an inappropriate number of values to a
   continuation not created by call-with-values, LET-VALUES, OR
   LET*-VALUES is undefined