From: Nicholas Clark <nick@ccl4.org>
Date: Thu, 13 Sep 2007 14:52:20 +0000 (+0000)
Subject: Note that list initialisation of state variables is TODO. While in the
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=636e63cb2d86040c1b02edfaea110c6993a0b8de;p=p5sagit%2Fp5-mst-13.2.git

Note that list initialisation of state variables is TODO. While in the
area, note how B::Deparse might be improved to name inlined constants.

p4raw-id: //depot/perl@31863
---

diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index d981521..1095a72 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -87,6 +87,28 @@ tests that are currently missing.
 
 A full test suite for the B module would be nice.
 
+=head2 Deparse inlined constants
+
+Code such as this
+
+    use constant PI => 4;
+    warn PI
+
+will currently deparse as
+
+    use constant ('PI', 4);
+    warn 4;
+
+because the tokenizer inlines the value of the constant subroutine C<PI>.
+This allows various compile time optimisations, such as constant folding
+and dead code elimination. Where these haven't happened (such as the example
+above) it ought be possible to make B::Deparse work out the name of the
+original constant, because just enough information survives in the symbol
+table to do this. Specifically, the same scalar is used for the constant in
+the optree as is used for the constant subroutine, so by iterating over all
+symbol tables and generating a mapping of SV address to constant name, it
+would be possible to provide B::Deparse with this functionality.
+
 =head2 A decent benchmark
 
 C<perlbench> seems impervious to any recent changes made to the perl core. It
@@ -526,6 +548,19 @@ calls during startup, and (by implication) a bit of tweaking of that order.
 These tasks would need C knowledge, and knowledge of how the interpreter works,
 or a willingness to learn.
 
+=head2 state variable initialization in list context
+
+Currently this is illegal:
+
+    state ($a, $b) = foo(); 
+
+The current Perl 6 design is that C<state ($a) = foo();> and
+C<(state $a) = foo();> have different semantics, which is tricky to implement
+in Perl 5 as currently the produce the same opcode trees. It would be useful
+to clarify that the Perl 6 design is firm, and then implement the necessary
+code in Perl 5. There are comments in C<Perl_newASSIGNOP()> that show the
+code paths taken by various assignment constructions involving state variables.
+
 =head2 Implement $value ~~ 0 .. $range
 
 It would be nice to extend the syntax of the C<~~> operator to also