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From: Ben Morrow on 30 Mar 2010 19:34 Quoth sreservoir <sreservoir(a)gmail.com>: > On 3/29/2010 10:19 PM, Ben Morrow wrote: > > > > perldoc aliased. > > No documentation found for "aliased". Well, no. It's a CPAN module, quite commonly used in some circles, which allows you to say use aliased "Some::Silly::Long::Class::Name" => "SomeClass"; my $x = SomeClass->new; It works by exporting a 'sub SomeClass' into the current package that simply returns the string "Some::Silly::Long::Class::Name", and relies on the fact that Perl will pick a sub over a package for a bareword if one exists. I find the whole concept makes me uneasy, especially since once you've said package Foo; use aliased "Some::Class" => "SomeClass"; you've effectively stomped on Foo::SomeClass from the point of view of the rest of the program. Ben
From: Ben Morrow on 30 Mar 2010 20:00 Quoth sreservoir <sreservoir(a)gmail.com>: > On 3/29/2010 10:26 PM, Ben Morrow wrote: > > > > Having a 'sub new' in scope is not uncommon: > > > > package Foo; > > > > sub new { ... } > > > > sub init { my $x = CGI->new(...) } > > > > 1; > > I haven't written an OO module for a long time, so this possibility > slipped my mind. however: > > % perl -MCGI -E 'sub new { die "wrong new" } say new CGI' > CGI=HASH(0x86f882c) There is no other possible interpretation for the bareword CGI here. If you also had a 'sub CGI' you would get new(CGI()) rather than CGI()->new(). Also, if you were calling 'method $object' rather than 'method Class' and there was a 'sub method' in scope you would get the sub call. > >> CGI->new chokes if there is a&CGI. might do bad things if CGI isn't > >> require'd or use'd. > > > > You mean 'if the CGI->new method isn't defined'. > > % perl -MCGI -MIO::Handle -E'sub CGI { IO::Handle:: } say CGI->new' > IO::Handle=GLOB(0x9ac1a20) > > I mean exactly what I said. I was responding to 'might do bad things if...'. ~% perl -e'sub CGI::new { warn "CGI->new" } CGI->new' CGI->new at -e line 1. No require or use there. The case where it does make a difference is (ironically) with the 'new CGI' syntax, where the presence of a 'require CGI' or 'use CGI' will prime the parser to try and make CGI into a classname rather than something else. > >> 'CGI'->new almost always does the right thing. > > > > use IO::Handle; > > warn "STDOUT"->blocking; > > > > Yes, this is 'the right thing' in this case, but not always. Just don't > > open a filehandle called 'CGI'. > > "almost"; in any case, none of the others would help you much if you did > have *CGI{IO}. Fair enough; also true. I don't believe there's any way to force interpretation as a class rather than a filehandle. > >> CGI::->new is syntactic sugar for 'CGI'->new. > > > > For CGI->new, except it ignores any 'sub CGI'. > > actually, both seem to be syntactic sugar for 'CGI'->, except CGI-> > does call a function if it exists. Well, both CGI:: and CGI-where-we-expect-a-classname are simply exceptions to strict 'subs' (which actually prevents barewords from being treated as unquoted strings, and has nothing to do with subs). However, CGI->new and "CGI"->new are at least slightly different: ~% perl -MO=Concise -e'CGI->new' 7 <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(main 1 -e:1) v:{ ->3 6 <1> entersub[t1] vKS/TARG ->7 3 <0> pushmark s ->4 4 <$> const(PV "CGI") sM/BARE ->5 5 <$> method_named(PV "new") ->6 -e syntax OK ~% perl -MO=Concise -e'"CGI"->new' 7 <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(main 1 -e:1) v:{ ->3 6 <1> entersub[t1] vKS/TARG ->7 3 <0> pushmark s ->4 4 <$> const(PV "CGI") sM ->5 5 <$> method_named(PV "new") ->6 -e syntax OK I don't know whether that extra '/BARE' makes any difference, though. Ben
From: sreservoir on 30 Mar 2010 20:19 On 3/30/2010 7:34 PM, Ben Morrow wrote: > > Quoth sreservoir<sreservoir(a)gmail.com>: >> On 3/29/2010 10:19 PM, Ben Morrow wrote: >>> >>> perldoc aliased. >> >> No documentation found for "aliased". > > Well, no. It's a CPAN module, quite commonly used in some circles, which > allows you to say > > use aliased "Some::Silly::Long::Class::Name" => "SomeClass"; > > my $x = SomeClass->new; > > It works by exporting a 'sub SomeClass' into the current package that > simply returns the string "Some::Silly::Long::Class::Name", and relies > on the fact that Perl will pick a sub over a package for a bareword if > one exists. I find the whole concept makes me uneasy, especially since > once you've said > > package Foo; > use aliased "Some::Class" => "SomeClass"; > > you've effectively stomped on Foo::SomeClass from the point of view of > the rest of the program. I suppose you could use some caller shenanigans with a closure, but. sub foo($$) { my $caller = caller; my $aliased = shift; my $package = shift; *$aliased = sub () { ((caller)->isa($caller))? $package : $aliased; } } of course, I don't understand what is so difficult about: $this = that::; $this->foo; -- "Six by nine. Forty two." "That's it. That's all there is." "I always thought something was fundamentally wrong with the universe."
From: Tad McClellan on 30 Mar 2010 20:33 Ben Morrow <ben(a)morrow.me.uk> wrote: > Quoth Justin C <justin.1003(a)purestblue.com>: >> $q = new CGI; > Method calls like > > new Class; > method $object; > method $object @args; # note the lack of comma after $object > > are in a form usually called 'indirect object syntax'[0]. This was added > into Perl when objects were first introduced (5.000, I believe), OP should see the docs section "Indirect Object Syntax" in perlobj.pod. But it contradicts Ben too: The other way to invoke a method is by using the so-called "indirect object" notation. This syntax was available in Perl 4 long before objects were introduced... -- Tad McClellan email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/" The above message is a Usenet post. I don't recall having given anyone permission to use it on a Web site.
From: sreservoir on 30 Mar 2010 20:37
On 3/30/2010 8:00 PM, Ben Morrow wrote: > > Quoth sreservoir<sreservoir(a)gmail.com>: >> On 3/29/2010 10:26 PM, Ben Morrow wrote: >>> >>> Having a 'sub new' in scope is not uncommon: >>> >>> package Foo; >>> >>> sub new { ... } >>> >>> sub init { my $x = CGI->new(...) } >>> >>> 1; >> >> I haven't written an OO module for a long time, so this possibility >> slipped my mind. however: >> >> % perl -MCGI -E 'sub new { die "wrong new" } say new CGI' >> CGI=HASH(0x86f882c) > > There is no other possible interpretation for the bareword CGI here. If > you also had a 'sub CGI' you would get new(CGI()) rather than > CGI()->new(). Also, if you were calling 'method $object' rather than > 'method Class' and there was a 'sub method' in scope you would get the > sub call. fair enough. >>>> CGI->new chokes if there is a&CGI. might do bad things if CGI isn't >>>> require'd or use'd. >>> >>> You mean 'if the CGI->new method isn't defined'. >> >> % perl -MCGI -MIO::Handle -E'sub CGI { IO::Handle:: } say CGI->new' >> IO::Handle=GLOB(0x9ac1a20) >> >> I mean exactly what I said. > > I was responding to 'might do bad things if...'. > > ~% perl -e'sub CGI::new { warn "CGI->new" } CGI->new' > CGI->new at -e line 1. > > No require or use there. The case where it does make a difference is > (ironically) with the 'new CGI' syntax, where the presence of a 'require > CGI' or 'use CGI' will prime the parser to try and make CGI into a > classname rather than something else. typically, you shouldn't define stuff int the namespace of a standard module. contrived counterexample, though, I suppose. >>>> 'CGI'->new almost always does the right thing. >>> >>> use IO::Handle; >>> warn "STDOUT"->blocking; >>> >>> Yes, this is 'the right thing' in this case, but not always. Just don't >>> open a filehandle called 'CGI'. >> >> "almost"; in any case, none of the others would help you much if you did >> have *CGI{IO}. > > Fair enough; also true. I don't believe there's any way to force > interpretation as a class rather than a filehandle. this is, incidentally, slightly ridiculous. % perl -E'sub STDOUT::a { die "right blocking" } say((*{STDOUT}{PACKAGE})->blocking);' Can't locate object method "blocking" via package "main" at -e line 2. um. >>>> CGI::->new is syntactic sugar for 'CGI'->new. >>> >>> For CGI->new, except it ignores any 'sub CGI'. >> >> actually, both seem to be syntactic sugar for 'CGI'->, except CGI-> >> does call a function if it exists. > > Well, both CGI:: and CGI-where-we-expect-a-classname are simply > exceptions to strict 'subs' (which actually prevents barewords from > being treated as unquoted strings, and has nothing to do with subs). > However, CGI->new and "CGI"->new are at least slightly different: I suppose it should be clarified that I meant it's syntactic sugar only in the 'suppose it's a classname' case. > ~% perl -MO=Concise -e'CGI->new' > 7<@> leave[1 ref] vKP/REFC ->(end) > 1<0> enter ->2 > 2<;> nextstate(main 1 -e:1) v:{ ->3 > 6<1> entersub[t1] vKS/TARG ->7 > 3<0> pushmark s ->4 > 4<$> const(PV "CGI") sM/BARE ->5 > 5<$> method_named(PV "new") ->6 > -e syntax OK > > ~% perl -MO=Concise -e'"CGI"->new' > 7<@> leave[1 ref] vKP/REFC ->(end) > 1<0> enter ->2 > 2<;> nextstate(main 1 -e:1) v:{ ->3 > 6<1> entersub[t1] vKS/TARG ->7 > 3<0> pushmark s ->4 > 4<$> const(PV "CGI") sM ->5 > 5<$> method_named(PV "new") ->6 > -e syntax OK > > I don't know whether that extra '/BARE' makes any difference, though. % perl -MO=Concise -e'CGI::->new' 7 <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(main 1 -e:1) v:{ ->3 6 <1> entersub[t1] vKS/TARG ->7 3 <0> pushmark s ->4 4 <$> const[PV "CGI"] sM/BARE ->5 5 <$> method_named[PV "new"] ->6 -e syntax OK maybe somebody who mangles the guts of perl can enlighten us? -- "Six by nine. Forty two." "That's it. That's all there is." "I always thought something was fundamentally wrong with the universe." |