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=head1 TITLE
Positional Return Lists Considered Harmful
=head1 VERSION
Maintainer: Jarkko Hietaniemi [EMAIL PROTECTED]
Date: 05 Aug 2000
Version: 2
Mailing List: [EMAIL PROTECTED]
Number: 37
=head1 ABSTRACT
Perl has traditionally returned from various functions long (2) lists
of values. Some traditions are simply bad.
=head1 DESCRIPTION
Functions like stat() and get*ent() return long lists of mysterious
values. The implementation is assumedly easy: just push some values
out of C structs into the Perl return stack.
Wrong. And once more, wrong.
Firstly, who can remember which one of the stat() return values was
the atime or which is the 4th return value of localtime()? The
perlfunc gmtime/localtime documentation makes this difficulty painfully
obvious by having to list the indices alongside the values.
Secondly, the current solution is seriously non-extensible. One
cannot easily add new return values to the APIs because someone may be
expecting an exact number of return values, or someone may be
accessing the values by position from the end of the list Obsoleting
values (or marking them as non-applicable to the current platform) has
to be done by for examples returning undef.
=head1 IMPLEMENTATION
The solution is simple: return hashes instead of lists. Yes, one
still has to know how the fields are named, so the proposed solution
is still not perfect.
=head2 THE AFFECTED FUNCTIONS
caller [1]
getgrent
getgrnam
getgrgid
gethostbyaddr
gethostbyname
gethostent
getnetbyaddr
getnetbyname
getnetent
getprotobyname
getprotobynumber
getprotoent
getpwent
getpwnam
getpwuid
getservbyname
getservbyport
getservent
gmtime
localtime
stat
[1] I guess the whole semantics and functionality of caller() is
severely up for grabs for Perl6.
For the get*() mafia, it is also debatable whether aping the C
interface is a good thing and worth preserving as such at all. The
preferred interface might be tied hashes. This interface might also
more naturally support non-POSIX operating systems with their own
native semantics, or POSIX operating systems with extended semantics
like higher security user databases.
=head1 REFERENCES
perlfunc
File::stat
User::grent
User::pwent
