From 88e1f1a2657a3a28cf3a7811902a09aca9e18986 Mon Sep 17 00:00:00 2001 From: Jesse Vincent Date: Thu, 5 Nov 2009 11:14:45 -0500 Subject: Implement facility to plug in syntax triggered by keywords Date: Tue, 27 Oct 2009 01:29:40 +0000 From: Zefram To: perl5-porters@perl.org Subject: bareword sub lookups Attached is a patch that changes how the tokeniser looks up subroutines, when they're referenced by a bareword, for prototype and const-sub purposes. Formerly, it has looked up bareword subs directly in the package, which is contrary to the way the generated op tree looks up the sub, via an rv2cv op. The patch makes the tokeniser generate the rv2cv op earlier, and dig around in that. The motivation for this is to allow modules to hook the rv2cv op creation, to affect the name->subroutine lookup process. Currently, such hooking affects op execution as intended, but everything goes wrong with a bareword ref where the tokeniser looks at some unrelated CV, or a blank space, in the package. With the patch in place, an rv2cv hook correctly affects the tokeniser and therefore the prototype-based aspects of parsing. The patch also changes ck_subr (which applies the argument context and checking parts of prototype behaviour) to handle subs referenced by an RV const op inside the rv2cv, where formerly it would only handle a gv op inside the rv2cv. This is to support the most likely kind of modified rv2cv op. [This commit includes the Makefile.PL for XS-APITest-KeywordRPN missing from the original patch, as well as updates to perldiag.pod and a MANIFEST sort] --- pod/perl5112delta.pod | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'pod/perl5112delta.pod') diff --git a/pod/perl5112delta.pod b/pod/perl5112delta.pod index 4d524670b3..ca8c8096ff 100644 --- a/pod/perl5112delta.pod +++ b/pod/perl5112delta.pod @@ -52,6 +52,28 @@ boolean, string or number of objects. It is invoked when an object appears on the right hand side of the C<=~> operator, or when it is interpolated into a regexp. See L. +=head2 Pluggable keywords + +Extension modules can now cleanly hook into the Perl parser to define new +kinds of keyword-headed expression and compound statement. The syntax +following the keyword is defined entirely by the extension. This allow +a completely non-Perl sublanguage to be parsed inline, with the right +ops cleanly generated. + +This feature is currently considered experimental, and using it to do +anything interesting is difficult. Many necessary supporting facilities, +such as the lexer and the pad system, can only be accessed through +unsupported internal interfaces. It is intended that the Perl 5.13 +development cycle will see the addition of clean, supported interfaces +for many of these functions. In Perl 5.12 most uses of pluggable keywords +will be via L. + +See L for the mechanism. The Perl core source +distribution also includes a new module L, which +implements reverse Polish notation arithmetic via pluggable keywords. +This module is mainly used for test purposes, and is not normally +installed, but also serves as an example of how to use the new mechanism. + =head1 New Platforms XXX List any platforms that this version of perl compiles on, that previous -- cgit v1.2.1