Referencing Control Operators

[John Baker]

Greetings.

Is it possible to reference a control operator?

For example, I'd like to take this code:


sub getFieldFromAllRecords {
my ($self, $directive, $keyword, $matchCondition) = @_;

my ($field, $regArr);

# another public method within same pkg:
my $allRecs = dumpAllAudits($self);
my %ar = %$allRecs;

push @{$regArr}, qr/$keyword/i;

my %select;
while( my($key, $value) = each(%ar)) {
map { next unless ($$value{$directive} =~ /$_/i); } @{$regArr};
$select{$key} = $$value{$directive};
}

return \%select;
}

and change it such that the 'unless' conditional operator is
referenced conceptually similar to the following:

sub getFieldFromAllRecords {
my ($self, $directive, $keyword, $matchCondition) = @_;

my $mc = $matchCondition; # changed: where $mc can be either
# 'if' or 'unless'.
my ($field, $regArr);

# another public method within same pkg:
my $allRecs = dumpAllAudits($self);
my %ar = %$allRecs;

push @{$regArr}, qr/$keyword/i;

my %select;
while( my($key, $value) = each(%ar)) {
map { next $mc ($$value{$directive} =~ /$_/i); } # changed
@{$regArr};
$select{$key} = $$value{$directive};
}

return \%select;
}

If it's not possible to reference operators, I'll rework the code.

Thanks in advance.
jab

[Mark Lobue]

At 12:12 PM 1/22/2004, John Baker wrote:

>Greetings.
>
>Is it possible to reference a control operator?
>
>For example, I'd like to take this code:
>
>
> sub getFieldFromAllRecords {
> my ($self, $directive, $keyword, $matchCondition) = @_;
>
> my ($field, $regArr);
>
> # another public method within same pkg:
> my $allRecs = dumpAllAudits($self);
> my %ar = %$allRecs;
>
> push @{$regArr}, qr/$keyword/i;
>
> my %select;
> while( my($key, $value) = each(%ar)) {
> map { next unless ($$value{$directive} =~ /$_/i); } @{$regArr};
> $select{$key} = $$value{$directive};
> }
>
> return \%select;
> }
>
>and change it such that the 'unless' conditional operator is
>referenced conceptually similar to the following:
>
> sub getFieldFromAllRecords {
> my ($self, $directive, $keyword, $matchCondition) = @_;
>

Rather than trying to write code into variables or self-modifying code, I think I would try defining some constants:

use constant MATCH_IF => 0;
use constant MATCH_UNLESS => 1;

Then assign $mc to MATCH_IF or MATCH_UNLESS any way you like

Then use xor:

map { next if ( ($$value{$directive} =~ /$_/i) xor $mc); } @{$regArr};

This is untested, but you get the idea.

-Mark

> my $mc = $matchCondition; # changed: where $mc can be either
> # 'if' or 'unless'.
> my ($field, $regArr);
>
> # another public method within same pkg:
> my $allRecs = dumpAllAudits($self);
> my %ar = %$allRecs;
>
> push @{$regArr}, qr/$keyword/i;
>
> my %select;
> while( my($key, $value) = each(%ar)) {
> map { next $mc ($$value{$directive} =~ /$_/i); } # changed
> @{$regArr};
> $select{$key} = $$value{$directive};
> }
>
> return \%select;
> }
>
>If it's not possible to reference operators, I'll rework the code.
>
>Thanks in advance.
>jab
>
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[Drieux]

On Jan 22, 2004, at 4:32 PM, Mark LoBue wrote:

> At 12:12 PM 1/22/2004, John Baker wrote:

[..]

>> and change it such that the 'unless' conditional operator is
>> referenced conceptually similar to the following:
>>
>> sub getFieldFromAllRecords {
>> my ($self, $directive, $keyword, $matchCondition) = @_;
>>

>
> Rather than trying to write code into variables or self-modifying
> code, I think I would try defining some constants:
>
> use constant MATCH_IF => 0;
> use constant MATCH_UNLESS => 1;
>
> Then assign $mc to MATCH_IF or MATCH_UNLESS any way you like
>
> Then use xor:
>
> map { next if ( ($$value{$directive} =~ /$_/i) xor $mc); } @{$regArr};
>
> This is untested, but you get the idea.

Fashionable and stylish as ever...

But it has the problem that it will cause a runtime error.
The following I think may help the OP:

use constant MATCH_IF => 0;
use constant MATCH_UNLESS => 1;

my @list = qw/foo Foo bar baz/;

my @foo = if_unless('foo',MATCH_IF,@list);

my @not_foo = if_unless('foo',MATCH_UNLESS,@list);

print "foo got $_\n" foreach(@foo);
print "not_foo got $_\n" foreach(@not_foo);

#------------------------
#
sub if_unless
{
my ($token, $mc, @list) = @_;

grep { $_ if ( ($token =~ /$_/i) xor $mc) } @list;

} # end of if_unless

generates:

foo got foo
foo got Foo
not_foo got bar
not_foo got baz

whereas changing the 'grep' to a 'map' will generate:

foo got foo
foo got Foo
foo got
foo got
not_foo got
not_foo got
not_foo got bar
not_foo got baz

so there is that point to take into account as to what one is
really trying to do here.

[..]

>> my %ar = %$allRecs;
>>
>> push @{$regArr}, qr/$keyword/i;
>>
>> my %select;
>> while( my($key, $value) = each(%ar)) {
>> map { next $mc ($$value{$directive} =~ /$_/i); } #
>> changed
>> @{$regArr};
>> $select{$key} = $$value{$directive};
>> }

[..]

now the minor question, why assign the %ar? you could
ahve done the while

while( my($key, $value) = each %$allRecs) {

minor nit.

So what exactly were you planning to assign the output
of that map to???

ciao
drieux

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