Formal comment #119 (enhancement)

Clarify the description of which continuations take multiple values
Reported by:	Alan Watson

Component:	baselibrary
Version:	5.91

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

RESPONSE:

This suggestion will be adopted in the next draft of the report.