Vincent Manis wrote:
\begin{rant}
On the subject of using void as a return value (rather than to indicate
that
a function or method doesn't return anything), EWWWW.
Please, please, don't ever write functions that return void as anything
other
than an indication that no value was returned.
#;44> (car (db-fetch-row (db-query "select salary where empname='Bilbo
Baggins'")))
#;45>
I don't yet have an opinion on using void, but this function would return either
a list: ( (void) )
or an alist: ( (salary . (void) )
depending on which we used to represent rows. Either way, there would indeed be
a return value.
So now, (a) you get no output, which might be mystifying and (b) car is
now returning
void. Neither of these violates any language rule, but each violates the
Law of
Least Astonishment.
For SQL nulls, one could use '(), as has been mentioned; alternatively,
an object
called the-SQL-null-object could be created (perhaps as a record type
value).
Incidentally, there are several different meanings for null in SQL,
including no
information, not applicable, no value presently exists (but one might in
the future),
etc. You can find lengthy essays on the appropriateness of using NULL in
several
of Chris Date's `Writings on Database' books. People have enough trouble
understanding
SQL null without further conflating it with `this function returns no
values'.
\end{rant}
Sorry :-) -- vincent
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