Re: RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
On Tue, 26 Sep 2000 11:13:30 -0700, Nathan Wiger wrote:
-{rwx}; # negation of a hashref
That's a weird hashref. Odd number of arguments, anyone?
If rwx is supposed to be a sub, we could say that this is an exception,
just like $hash{bareword} is an exception. So, if you want the sub, use
parens:
-{rwx()}
Need I still say that this one is my favourite? :-)
--
Bart.
Re: RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
On Tue, 26 Sep 2000, Nathan Wiger wrote: John Porter wrote: Yeah, not to mention the fact that many modules, notably CGI.pm, are arranged to allow to use unquoted strings of the form -name: print textfield( -name = 'description' ); Well, this one's not an issue, because = auto-quotes the LHS. It's the same as this: print textfield( "-name", 'description' ); Actually, more like this: print textfield( -'name', 'description' ); Try putting it through -MO=Deparse. I guess the quoting behaviour of = "binds" more strongly than the hyphen, so that "-name =" is interpreted as unary minus + bareword 'name' + big arrow, leading to unary minus + quoted bareword 'name' + big arrow, which is equivalent to - "name" and a comma. Fortunately, - "string" doesn't convert "string" to a number (0) and then apply negation but results in "-string" (`perldoc perlop` says: "If the operand is an identifier, a string consisting of a minus sign concatenated with the identifier is returned. [...] One effect of these rules is that `-bareword' is equivalent to `"-bareword"'." Cheers, Philip -- Philip Newton [EMAIL PROTECTED]
Re: RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
On Tue, Sep 26, 2000 at 05:53:13AM -, Nate Wiger wrote:
Currently, file tests cannot be grouped, resulting in very long
expressions when one wants to check to make sure some thing is a
readable, writeable, executable directory:
if ( -d $file -r $file -w $file -x $file ) { ... }
Non-novice perl programmers would probably write this as you have
below with the special _ filehandle. Perhaps you should move that to
the fore and comment on it's unreadability and general ickiness :-)
It would be really nice if these could be grouped instead:
if ( -drwx $file ) { ... }
Indeed it would.
-Scott
--
Jonathan Scott Duff
[EMAIL PROTECTED]
Re: RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
On 26 Sep 2000, Perl6 RFC Librarian wrote:
=head1 TITLE
Allow grouping of -X file tests and add Cfiletest builtin
Nice summary. Thanks.
=head1 IMPLEMENTATION
This would involve making C-[a-zA-Z]+ a special token in all contexts,
serving as a shortcut for the Cfiletest builtin.
=head1 MIGRATION
There is a subtle trap if you are negating subroutines:
$result = -drwx $file;
And expect this to be parsed like this:
$result = - drwx($file);
However, usage such as this is exceedingly unlikely, and can simply be
resolved by the p52p6 translator looking for C-([a-zA-Z]{2,}) and
replacing it with C- $1, since injecting a single space will break up
the token.
I can't believe that special-casing the token -[rwxoRWXOezsfdlpSbctugkTBMAC]+
is an acceptble solution. I mean think of all the existing perl keywords
that that already matches: -pos, -cos, -lc, -uc, -fork, -use, -pop, -exp,
-oct, -log, -ord + others!. A lot of these already have a legitimate
not-filetest meaning, others not :-) So it still seems to me that some
sort of disambiguating syntax is needed, if not actually findable, to
save this filetest grouping idea of mine from the scrap heap. I guess
the p5-to-p6 converter could still resolve this as you stated, but I just
don't like it...
John.
Re: RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
John L. Allen wrote: I can't believe that special-casing the token -[rwxoRWXOezsfdlpSbctugkTBMAC]+ is an acceptble solution. I mean think of all the existing perl keywords that that already matches: -pos, -cos, -lc, -uc, -fork, -use, -pop, -exp, -oct, -log, -ord + others!. A lot of these already have a legitimate not-filetest meaning, others not :-) Yeah, not to mention the fact that many modules, notably CGI.pm, are arranged to allow to use unquoted strings of the form -name: print textfield( -name = 'description' ); -- John Porter Aus des Weltalls ferne funken Radiosterne.
RFC 320 (v1) Allow grouping of -X file tests and add Cfiletest builtin
This and other RFCs are available on the web at
http://dev.perl.org/rfc/
=head1 TITLE
Allow grouping of -X file tests and add Cfiletest builtin
=head1 VERSION
Maintainer: Nathan Wiger [EMAIL PROTECTED]
Date: 25 Sep 2000
Mailing List: [EMAIL PROTECTED]
Number:
320
Status: Developing
=head1 ABSTRACT
Currently, file tests cannot be grouped, resulting in very long
expressions when one wants to check to make sure some thing is a
readable, writeable, executable directory:
if ( -d $file -r $file -w $file -x $file ) { ... }
It would be really nice if these could be grouped instead:
if ( -drwx $file ) { ... }
Notice how much easier this is to read and write.
=head1 DESCRIPTION
=head2 File Test Grouping
See above. Multiple file tests, when grouped, should be ANDed together.
This RFC does not propose a way to OR them, since usage like this:
if ( -d $file || -r $file || -w $file || -x $file ) { ... }
Is highly uncommon, to say the least.
Notice this has the nice side effect of eliminating the need for C_ in
many cases, since this:
if ( -d $file -r _ -w _ -x _ ) { ... }
Can simply be written as a single grouped file test, as shown above. If
you need to check for more complex logic, you still have to do that
separately:
if ( -drwx $file and ! -h $file ) { ... }
This is the simplest and also probably the clearest way to implement
this.
=head2 New Cfiletest Builtin
This RFC also proposes a new Cfiletest builtin that is actually what
is used for these tests. The C-[a-zA-Z]+ form is simply a shortcut to
this builtin, just like is a shortcut to Creadline. So:
if ( -rwdx $file ) { ... }
Is really just a shortcut to the Cfiletest builtin:
if ( filetest $file, 'rwdx' ) { ... }
Either form could be used, depending on the user's preferences (just
like Creadline).
=head1 IMPLEMENTATION
This would involve making C-[a-zA-Z]+ a special token in all contexts,
serving as a shortcut for the Cfiletest builtin.
=head1 MIGRATION
There is a subtle trap if you are negating subroutines:
$result = -drwx $file;
And expect this to be parsed like this:
$result = - drwx($file);
However, usage such as this is exceedingly unlikely, and can simply be
resolved by the p52p6 translator looking for C-([a-zA-Z]{2,}) and
replacing it with C- $1, since injecting a single space will break up
the token.
=head1 REFERENCES
This grew out of a discussion on RFC 290 between myself, John Allen,
Clayton Scott, Bart Lateur, and others
