This and other RFCs are available on the web at http://dev.perl.org/rfc/ =head1 TITLE Data: sprintf() with overloaded objects =head1 VERSION Maintainer: Ilya Zakharevich <[EMAIL PROTECTED]> Date: 15 September 2000 Mailing List: [EMAIL PROTECTED] Number: 235 Version: 1 Status: Developing =head1 ABSTRACT This RFC proposes a support of sprintf() with overloaded objects; =head1 DESCRIPTION The problems: =over =item * too many different flavors to support, many of them equivalent; =item * Many different flags, a lot of work to implement them all. =item * C<*> in the flags. =back One would want an interface which allows to get acceptable results with a minimal of work, but also allows as fine control as possible if needed. The solution: =over =item * merge many flavors into groups, with one overloaded operation per group. For example, C<'%i'> and C<'%d'> should invoke the same overloaded operation keyed by C<%d> (or C<%?d>, see below). =item * provide the actual letter (and flags!) as an argument to disambiguate it inside the group; =item * provide I<two> operations to overload per group (only one of them should be used), for example C<'%+040d'> should invoke the operation keyed by C<'%?d'> if present, otherwise one keyed by C<'%d'>, then would postprocess the results. Similarly, C<'%d'> should invoke the operation keyed by C<'%d'> if present, otherwise one keyed by C<'%d'>. =item * If C<*> is present in the flags, the count is provided as an additional argument to the corresponding method. (One additional argument per each C<*>.) =back For example, if method C<'%d'> is overloaded by the method C<FORMAT_D>, and C<'%?d'> is not overloaded, then sprintf('%s %0*i %s', '--', $overloaded_object, 10, '--') calls $overloaded_object->FORMAT_D('0*i', 10); and postprocesses the result. =head1 Composite objects The "standard" semantic of processing flags in the overloaded methods for composite objects (such as complex numbers or vectors) should be: delegate the flags to components "as is". (As opposed to applying widths to the I<total> field.) There may be obvious exceptions: for complex numbers C<+>/C<-> before the imaginary part is needed, but if one inserts this sign no matter what, the format C<'%+10i'> would result in a double C<+> sign or C<+-> or C<-->. The other approach of prepending C<'+'> to the flags no matter what would omit space for the format C<'% 10i'>. =head1 MIGRATION ISSUES NONE =head1 IMPLEMENTATION More or less straightforward =head1 REFERENCES RFC ???
