Author: larry
Date: Fri Feb 2 01:07:36 2007
New Revision: 13564
Modified:
doc/trunk/design/syn/S03.pod
doc/trunk/design/syn/S12.pod
Log:
Also allow colon pair syntax for a methodlike kind of filetest.
A bit of junctional cleanup.
Modified: doc/trunk/design/syn/S03.pod
==============================================================================
--- doc/trunk/design/syn/S03.pod (original)
+++ doc/trunk/design/syn/S03.pod Fri Feb 2 01:07:36 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 8 Mar 2004
- Last Modified: 1 Feb 2007
+ Last Modified: 2 Feb 2007
Number: 3
- Version: 95
+ Version: 96
=head1 Overview
@@ -29,7 +29,7 @@
Level Examples
===== ========
Terms 42 3.14 "eek" qq["foo"] $x :!verbose
- Method postfix .meth .+ .? .* .() .[] .{} .<> .«» .:: .= .^
+ Method postfix .meth .+ .? .* .() .[] .{} .<> .«» .:: .= .^ .:
Autoincrement ++ --
Exponentiation **
Symbolic unary ! + - ~ ? $ @ % & | +^ ~^ ?^ \ ^ =
@@ -1408,12 +1408,23 @@
=item *
-The filetest operators are gone. We now use a Pair as a pattern to
-get the same effect:
+The filetest operators are gone. We now use a Pair as either a
+pattern or a method name to get the same effect:
if $filename ~~ :e { say "exists" }
+ if $filename.:e { say "exists" }
-These tests may be combined via junctions:
+Both of these forms actually translate to
+
+ if $filename.TEST(:e) { say "exists" }
+
+which which is a generic mechanism that dispatches to the object's
+class to find the definition of C<TEST>. (It just happens that C<Str>
+(filenames) and C<IO> (filehandles) default to the expected filetest
+semantics, but C<$regex.:i> might tell you whether the regex is case
+insensitive, for instance.)
+
+Using the pattern form, multiple tests may be combined via junctions:
given $handle {
when all :r :w :x {...}
@@ -1421,14 +1432,24 @@
when * {...}
}
+The advantage of the method form is that it can be used in places that
+require tighter precedence than C<~~> provides:
+
+ sort { $^a.:M <=> $^b.:M }, @files
+
+though that's a silly example since you could just write:
+
+ sort { .:M }, @files
+
+But that demonstrates the other advantage of the method form.
+
In general, the user need not worry about caching the stat buffer.
-The stat buffer will automatically be reused if the same object is
-queried and the stat buffer has not "expired", where that is defined
-as older than a second or so. If this is a concern, an explicit stat()
-or lstat() will automatically reset the stat buffer, as will switching
-to a different filename or handle.
+The stat buffer will automatically be reused if the same object has
+recently been queried, where "recently" is defined as less than a
+second or so. If this is a concern, an explicit stat() or lstat()
+on that file will automatically reset the stat buffer for that file.
-Note that C<$file ~~ :s> still returns the filesize, but C<:!s> is true
+Note that C<:s> still returns the filesize, but C<:!s> is true
only if the file is of size 0.
=item *
@@ -1832,10 +1853,14 @@
Junctions are specifically unordered. So if you say
- for all(@foo) {...}
+ foo() | bar() | baz() == 42
-it indicates to the compiler that there is no coupling between loop
-iterations and they can be run in any order or even in parallel. XXX bogus
+it indicates to the compiler that there is no coupling between
+the junctional arguments. They can be evaluated in any order or in
+parallel. They can short-circuit as soon as any of them return 42,
+and not run the others at all. Or if running in parallel, the first
+successful thread may terminate the other threads abruptly. In general
+you probably want to avoid code with side effects in junctions.
Use of negative operators with syntactically recognizable junctions may
produce a warning on code that works differently in English than in Perl.
Modified: doc/trunk/design/syn/S12.pod
==============================================================================
--- doc/trunk/design/syn/S12.pod (original)
+++ doc/trunk/design/syn/S12.pod Fri Feb 2 01:07:36 2007
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 27 Oct 2004
- Last Modified: 1 Feb 2007
+ Last Modified: 2 Feb 2007
Number: 12
- Version: 36
+ Version: 37
=head1 Overview
@@ -607,6 +607,27 @@
my Dog $spot .= new(:tail<LONG> :legs<SHORT>);
+=head1 Pair query methods
+
+Certain classes such as filehandles allow colon pairs to be used as if they
+were methods. When you say:
+
+ $filehandle.:e
+ $filehandle.:!x
+
+it actually calls
+
+ $filehandle.TEST(:e)
+ $filehandle.TEST(:!x)
+
+which is expected to return a value that can be used as a boolean.
+While this is primarily intended for use by file tests, other classes
+may define a C<TEST> method to provide a similar mechanism for interrogating
+lightweight properties without having to define methods for all of them.
+(Note, though, that I<all> such queries are answered by the first located
+C<TEST> method--they are not inherited independently. The C<TEST> method
+must explicitly pass the query on to other classes in such cases.)
+
=head1 Calling sets of methods
For any method name, there may be some number of candidate methods
