Author: autrijus
Date: Sun Mar 12 05:16:44 2006
New Revision: 8123
Modified:
doc/trunk/design/syn/S06.pod
Log:
* S06: Patch from bsb++ to make macros hygienic by default,
with TimToady++'s idea for q:code(:COMPILING) to denote
unhygienicness.
Modified: doc/trunk/design/syn/S06.pod
==============================================================================
--- doc/trunk/design/syn/S06.pod (original)
+++ doc/trunk/design/syn/S06.pod Sun Mar 12 05:16:44 2006
@@ -1985,6 +1985,11 @@
return q:code < say $a + <<< $ast >>> >
return q:code ( say $a + ((( $ast ))) )
+The delimiters don't have to be bracketing quotes, but the following
+is probably to be construed as Bad Style:
+
+ return q:code / say $a + /// $ast /// /
+
(Note to implementors: this must not be implemented by finding
the final closing delimiter and preprocessing, or we'll violate our
one-pass parsing rule. Perl 6 parsing rules are parameterized to know
@@ -1997,12 +2002,7 @@
inner expression, the inner parser rule is parameterized to know that
C<}}}> or whatever is its closing delimiter.)
-The delimiters don't have to be bracketing quotes, but the following
-is probably to be construed as Bad Style:
-
- return q:code / say $a + /// $ast /// /
-
-Dequoted expressions are inserted appropriately depending on the
+Unquoted expressions are inserted appropriately depending on the
type of the variable, which may be either a syntax tree or a string.
(Again, syntax tree is preferred.) The case is similar to that of a
macro called from within the quasiquote, insofar as reparsing only
@@ -2020,10 +2020,20 @@
(Generally, a term expects a following postfix or infix operator,
and an operator expects a following term or prefix operator.)
-A quasiquote is not a block (even if the delimiters are curlies),
-so any declaration of a variable is taken to be part of the block
-surrounding the macro call location. Add your own {...} if you want
-a block to surround your declarations.
+Quasiquotes default to hygienic lexical scoping, just like closures.
+The visibility of lexical variables is limited to the q:code expression
+by default. A variable declaration can be made externally visible using
+the C<COMPILING::> pseudo-package. Individual variables can be made visible,
+or all top-level variable declarations can be exposed using the
+C<q:code(:COMPILING)> form.
+
+Both examples below will add C<$new_variable> to the lexical scope of
+the macro call:
+
+ q:code { my $COMPILING::new_variable; my $private_var; ... }
+ q:code(:COMPILING) { my $new_variable; { my $private_var; ... } }
+
+(Note that C<:COMPILING> has additional effects described in L<Macros>.)
=head1 Other matters
