How do I call sort with an anonymous subroutine stored in a hash ??

[Casey]

Hi, I haven't being using perl for too long. Can someone explain the
correct way to get the sort function to recognize an anonymous function
declared as a hash value? Look at my sample code for clarification:

#!/usr/bin/perl

@my_array = qw( g a z f u q m i e b );
$hash{my_sort_s ub} = sub { $a cmp $b };
$hash{test_rout ine} = sub { print "test_routi ne works\n" };
&{$hash{test_ro utine}};
print @my_array;
print "\n";
print( sort &{$hash{my_sort _sub}} @my_array );
print "\n";


The code fails to compile with error:

Array found where operator expected at ./test.pl line 9, near "} "
(Missing operator before ?)
syntax error at ./test.pl line 9, near "} @my_array "
Execution of ./test.pl aborted due to compilation errors.

Help! I don't see what's wrong with this.

[nobull@mail.com]

Re: How do I call sort with an anonymous subroutine stored in a hash ??

Casey <mail@nowhere.c om> wrote in message news:<pan.2004. 01.30.07.28.21. 56357@nowhere.c om>...[color=blue]
> Can someone explain the
> correct way to get the sort function to recognize an anonymous function
> declared as a hash value?[/color]

AFAIK, you cannot. It's one of those nasty corners of Perl syntax
where to do the "right thing" would require unlimited lookahead (or
roll-back) in the parser. Perl doesn't even try - it's just
documented as a limitation.
[color=blue]
> print( sort &{$hash{my_sort _sub}} @my_array );[/color]

my $sort_sub = $hash{my_sort_s ub};
print( sort $sort_sub @my_array );
[color=blue]
> Array found where operator expected at ./test.pl line 9, near "} "
> (Missing operator before ?)
> syntax error at ./test.pl line 9, near "} @my_array "[/color]
[color=blue]
> Help! I don't see what's wrong with this.[/color]

The syntax of the Perl sort function is explained in

perldoc -f sort

This newsgroup does not exist (see FAQ). Please do not start threads
here.

[Anthony]

Re: How do I call sort with an anonymous subroutine stored in a hash ??

you are dereferencing the anonymous subroutine incorrectly.

On line 9 you have:
print( sort &{$hash{my_sort _sub}} @my_array );

It should be:
print( sort {&{$hash{my_sor t_sub}}} @my_array );

hope this helps,
Anthony



Casey <mail@nowhere.c om> wrote in message news:<pan.2004. 01.30.07.28.21. 56357@nowhere.c om>...[color=blue]
> Hi, I haven't being using perl for too long. Can someone explain the
> correct way to get the sort function to recognize an anonymous function
> declared as a hash value? Look at my sample code for clarification:
>
> #!/usr/bin/perl
>
> @my_array = qw( g a z f u q m i e b );
> $hash{my_sort_s ub} = sub { $a cmp $b };
> $hash{test_rout ine} = sub { print "test_routi ne works\n" };
> &{$hash{test_ro utine}};
> print @my_array;
> print "\n";
> print( sort &{$hash{my_sort _sub}} @my_array );
> print "\n";
>
>
> The code fails to compile with error:
>
> Array found where operator expected at ./test.pl line 9, near "} "
> (Missing operator before ?)
> syntax error at ./test.pl line 9, near "} @my_array "
> Execution of ./test.pl aborted due to compilation errors.
>
> Help! I don't see what's wrong with this.[/color]

[Casey]

Re: How do I call sort with an anonymous subroutine stored in a hash ??

On Fri, 30 Jan 2004 04:03:25 -0800, nobull wrote:
[color=blue]
> Casey <mail@nowhere.c om> wrote in message news:<pan.2004. 01.30.07.28.21. 56357@nowhere.c om>...[color=green]
>> Can someone explain the
>> correct way to get the sort function to recognize an anonymous function
>> declared as a hash value?[/color]
>
> AFAIK, you cannot. It's one of those nasty corners of Perl syntax
> where to do the "right thing" would require unlimited lookahead (or
> roll-back) in the parser. Perl doesn't even try - it's just
> documented as a limitation.
>[color=green]
>> print( sort &{$hash{my_sort _sub}} @my_array );[/color]
>
> my $sort_sub = $hash{my_sort_s ub};
> print( sort $sort_sub @my_array );
>[color=green]
>> Array found where operator expected at ./test.pl line 9, near "} "
>> (Missing operator before ?)
>> syntax error at ./test.pl line 9, near "} @my_array "[/color]
>[color=green]
>> Help! I don't see what's wrong with this.[/color]
>
> The syntax of the Perl sort function is explained in
>
> perldoc -f sort
>
> This newsgroup does not exist (see FAQ). Please do not start threads
> here.[/color]

Thanks for the solution. Have a good day.