diff options
| -rwxr-xr-x | embed.pl | 1 | ||||
| -rw-r--r-- | pod/perldata.pod | 8 | ||||
| -rw-r--r-- | pod/perldelta.pod | 49 |
3 files changed, 44 insertions, 14 deletions
@@ -838,6 +838,7 @@ START_EXTERN_C EOT # functions that take va_list* for implementing vararg functions +# NOTE: makedef.pl must be updated if you add symbols to %vfuncs my %vfuncs = qw( Perl_croak Perl_vcroak Perl_warn Perl_vwarn diff --git a/pod/perldata.pod b/pod/perldata.pod index 067c6d9bd5..0b83214a73 100644 --- a/pod/perldata.pod +++ b/pod/perldata.pod @@ -648,8 +648,12 @@ You couldn't just loop through C<values %hash> to do this because that function produces a new list which is a copy of the values, so changing them doesn't change the original. -As a special rule, if a list slice would produce a list consisting -entirely of undefined values, the null list is produced instead. +A slice of an empty list is still an empty list. Thus: + + @a = ()[1,0]; # @a has no elements + @b = (@a)[0,1]; # @b has no elements + @b = (1,undef)[1,0,1]; # @b has three elements + This makes it easy to write loops that terminate when a null list is returned: diff --git a/pod/perldelta.pod b/pod/perldelta.pod index c34897f7f3..88eeffc9c6 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -24,6 +24,31 @@ responsibility to ensure that warnings are enabled judiciously. =over 4 +=item Treatment of list slices of undef has changed + +When taking a slice of a literal list (as opposed to a slice of +an array or hash), Perl used to return an empty list if the +result happened to be composed of all undef values. + +The new behavior is to produce an empty list if (and only if) +the original list was empty. Consider the following example: + + @a = (1,undef,undef,2)[2,1,2]; + +The old behavior would have resulted in @a having no elements. +The new behavior ensures it has three undefined elements. + +Note in particular that the behavior of slices of the following +cases remains unchanged: + + @a = ()[1,2]; + @a = (getpwent)[7,0]; + @a = (anything_returning_empty_list())[2,1,2]; + @a = @b[2,1,2]; + @a = @c{'a','b','c'}; + +See L<perldata>. + =item Possibly changed pseudo-random number generator In 5.005_0x and earlier, perl's rand() function used the C library @@ -72,11 +97,11 @@ returned values, but this is can make a significant difference when creating references to the returned values. Keys in the hash are still returned as copies when iterating on -on a hash. +a hash. =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS -vec() generates a run-time error if the BITS arguments is not +vec() generates a run-time error if the BITS argument is not a valid power-of-two integer. =item Text of some diagnostic output has changed @@ -550,7 +575,7 @@ change#2150 change#4052 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>] -=head2 Experimental support form user-hooks in @INC +=head2 Experimental support for user-hooks in @INC [TODO - Ken Fox <kfox@ford.com>] @@ -565,7 +590,7 @@ See L<perlsub/"Overriding Built-in Functions">. =head2 New variable $^C reflects C<-c> switch -C<$^C> contains a boolean that reflects whether perl is being run +C<$^C> has a boolean value that reflects whether perl is being run in compile-only mode (i.e. via the C<-c> switch). Since BEGIN blocks are executed under such conditions, this variable enables perl code to determine whether actions that make sense @@ -625,9 +650,9 @@ that was encountered. The mechanism for reporting such errors has been reimplemented to queue compile-time errors and report them at the end of the compilation as true errors rather than as warnings. This fixes -error messages that used to leak through as warnings when code -was compiled at run time using C<eval STRING>, and allows such -errors to be reliably trapped using __DIE__ hooks. +cases where error messages leaked through in the form of warnings +when code was compiled at run time using C<eval STRING>, and +also allows such errors to be reliably trapped using __DIE__ hooks. =head2 Automatic flushing of output buffers @@ -686,7 +711,7 @@ the specified value exists, not merely if the key is valid. =head2 C<goto &sub> and AUTOLOAD -C<goto &sub> construct works correctly when C<&sub> happens +The C<goto &sub> construct works correctly when C<&sub> happens to be autoloaded. =head2 C<-bareword> allowed under C<use integer> @@ -702,7 +727,7 @@ Constructs such as C<($a ||= 2) += 1> are now allowed. =head2 C<sort $coderef @foo> allowed sort() did not accept a subroutine reference as the comparison -function in earlier versions. This has been fixed. +function in earlier versions. This is now permitted. =head2 Failures in DESTROY() @@ -754,7 +779,7 @@ cause silent failures. This has been fixed. Prior versions used to run BEGIN B<and> END blocks when Perl was run in compile-only mode. Since this is typically not the expected -behavior, END blocks are not executed when the C<-c> switch +behavior, END blocks are not executed anymore when the C<-c> switch is used. Note that something resembling the previous behavior can still be @@ -798,7 +823,7 @@ semantics in later versions of Perl. =head2 Simple sort() using { $a <=> $b } and the like are optimized -Many common sort() opertions using a simple inlined block are now +Many common sort() operations using a simple inlined block are now optimized for faster performance. =head2 Optimized assignments to lexical variables @@ -1051,7 +1076,7 @@ comparison functions. See L<File::Compare>. File::Find now works correctly when the wanted() function is either autoloaded or is a symbolic reference. -A bug that cause File::Find to lose track of the working directory +A bug that caused File::Find to lose track of the working directory when pruning top-level directories has been fixed. =item File::Spec |