Author: jdlugosz
Date: 2009-05-26 02:14:51 +0200 (Tue, 26 May 2009)
New Revision: 26938
Modified:
docs/Perl6/Spec/S04-control.pod
Log:
[S04] update code under "do-once loop" in line with current specs.
Move a paragraph that was interfering with the antecedent of the following
paragraph.
Modified: docs/Perl6/Spec/S04-control.pod
===================================================================
--- docs/Perl6/Spec/S04-control.pod 2009-05-25 23:55:20 UTC (rev 26937)
+++ docs/Perl6/Spec/S04-control.pod 2009-05-26 00:14:51 UTC (rev 26938)
@@ -518,27 +518,23 @@
statement, or if you want to attach multiple statements. you must either
use the curly form or surround the entire expression in brackets of some sort:
- @primes = (do (do $_ if .prime) for 1..100);
+ @primes = do $_ if prime($_) for 1..100;
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<$> operator in Haskell. That is,
precedence decisions do not cross a C<do> boundary, and the missing
"right paren" is assumed at the next statement terminator or unmatched
-bracket. A C<do> is assumed immediately after any opening bracket,
+bracket. A C<do> is unnecessary immediately after any opening bracket as
+the syntax inside brackets is a semicolon-separated list of statements,
so the above can in fact be written:
- @primes = (($_ if .prime) for 1..100);
+ @primes = ($_ if prime($_) for 1..100);
This basically gives us list comprehensions as rvalue expressions:
- (for 1..100 { $_ if .prime}).say
+ (for 1..100 { $_ if prime($_)}).say
-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
-useful for the do-once block, since it is offically a loop and can take
-therefore loop control statements.
-
Another consequence of this is that any block just inside a
left parenthesis is immediately called like a bare block, so a
multidimensional list comprehension may be written using a block with
@@ -550,6 +546,11 @@
@names = ({ "$^name.$^num" } for 'a'..'zzz' X 1..100);
+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
+useful for the do-once block, since it is offically a loop and can take
+therefore loop control statements.
+
=head2 Statement-level bare blocks
Although a bare block occuring as a single statement is no longer
