Section 2.4 of the Haskell 98 report says
"Compilers that offer warnings for unused identifiers are encouraged
to suppress such warnings for identifiers beginning with underscore.
This allows programmers to use ``_foo'' for a parameter they expect
to be unused."
In GHC at least, a frequent idiom is the following:
case e of
-- ... other alternatives omitted
other -> default_action
Here other is not free in default_action.
Unfortunately, the H98 recommended behaviour yields a warning for the
unused identifier `other' here.
The question is: should there be special syntax for `all remaining
cases' (`else', `other', or `otherwise', for example)? This would not
require a new reserved word; it would merely require an addition to
the above recommendation that warnings be suppressed for identifiers
with this name also.
Alternatively, of course, the coding style could simply change to
case e of
-- ...
_other -> default_action
or
case e of
-- ...
_ -> default_action
The former is IMHO ugly, and the latter fails to indicate to the
reader that this is intended to match not *all* alternatives, but just
those not already matched.
--KW 8-)
