Author: larry
Date: Tue Aug 15 08:52:46 2006
New Revision: 10971
Modified:
doc/trunk/design/syn/S04.pod
Log:
Clarifications on C<do> with bare expression.
Modified: doc/trunk/design/syn/S04.pod
==============================================================================
--- doc/trunk/design/syn/S04.pod (original)
+++ doc/trunk/design/syn/S04.pod Tue Aug 15 08:52:46 2006
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 19 Aug 2004
- Last Modified: 14 Aug 2006
+ Last Modified: 15 Aug 2006
Number: 4
- Version: 34
+ Version: 35
This document summarizes Apocalypse 4, which covers the block and
statement syntax of Perl.
@@ -349,8 +349,15 @@
$x = do if $a { $b } else { $c };
-This construct only allows you to prefix a statement. If you want to
-continue the expression after the statement you must use the curly form.
+This construct only allows you to attach a single statement to the end
+of an expression. If you want to continue the expression after the
+statement, or if you want to attach multiple statements. you must use
+the curly form. Since a bare expression may be used as a statement,
+you may use C<do> on an expression, but its only effect is to function
+as an unmatched left parenthesis, much like the C<$> operator in
+Haskell. That is, precedence decisions do not cross a C<do> boundary.
+Conjectural: a C<do> may be used within a subexpression, but only if
+terminated by an unmatched right bracket of some kind.
Since C<do> is defined as going in front of a statement, it follows
that it can always be followed by a statement label. This is particularly
