running sub via string while using strict. 1

[1DMF]

Hi,

I'm trying to dynamically call a subroutine, only i get an error when using

&{'page'.$id.'_data'}();

Saying not while strict is on, if I turn strict off, the command runs as desired.

Is there any other way of dynamically calling a sub while using strict?

Thanks,
1DMF

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[1DMF]

I checked out the strict pragma and found I can turn off strict refs with

no strict "refs";

Can someone advise what else I'm now stopping from showing as an error apart from the dynamic routine call, I have always worked under full strict , so am concerned what other potential 'bugs' this may introduce.

Cheers,
1DMF

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[mikrom]

This reminds me on similar topic discussed back in 2006 in this thread:

http://www.tek-tips.com/viewthread.cfm?qid=1294921

The final aspect of the use strict pragma is the disabling of soft references (or symbolic references).

(see here:

http://www.stonehenge.com/merlyn/UnixReview/col54.html)

Here is the example for using soft references:
soft_ref.pl

[COLOR=#0000ff]# Example of using soft refernces[/color]
[COLOR=#0000ff]# works only without strict-pragma[/color]

[COLOR=#0000ff]#use strict;[/color]
[COLOR=#804040][b]use warnings[/b][/color];

[COLOR=#804040][b]sub[/b][/color][COLOR=#008080] [/color][COLOR=#008080]addition[/color]{
  [COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]$a[/color], [COLOR=#008080]$b[/color]) = [COLOR=#008080]@_[/color];
  [COLOR=#804040][b]return[/b][/color] ([COLOR=#008080]$a[/color]+[COLOR=#008080]$b[/color]);
}

[COLOR=#804040][b]sub[/b][/color][COLOR=#008080] [/color][COLOR=#008080]substraction[/color]{
  [COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]$a[/color], [COLOR=#008080]$b[/color]) = [COLOR=#008080]@_[/color];
  [COLOR=#804040][b]return[/b][/color] ([COLOR=#008080]$a[/color]-[COLOR=#008080]$b[/color]);
}

[COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]$foo[/color], [COLOR=#008080]$bar[/color]);

[COLOR=#008080]$a[/color] = [COLOR=#ff00ff]1[/color]; [COLOR=#008080]$b[/color] = [COLOR=#ff00ff]2[/color];
[COLOR=#0000ff]#[/color]
[COLOR=#008080]$foo[/color]=[COLOR=#ff00ff]'[/color][COLOR=#ff00ff]addition[/color][COLOR=#ff00ff]'[/color];
[COLOR=#008080]$bar[/color]=[COLOR=#008080]&$foo[/color]([COLOR=#008080]$a[/color],[COLOR=#008080]$b[/color]);
[COLOR=#804040][b]print[/b][/color] [COLOR=#ff00ff]"[/color][COLOR=#6a5acd]\$[/color][COLOR=#ff00ff]bar=[/color][COLOR=#008080]$bar[/color][COLOR=#6a5acd]\n[/color][COLOR=#ff00ff]"[/color];
[COLOR=#0000ff]#[/color]
[COLOR=#008080]$foo[/color]=[COLOR=#ff00ff]'[/color][COLOR=#ff00ff]substraction[/color][COLOR=#ff00ff]'[/color];
[COLOR=#008080]$bar[/color]=[COLOR=#008080]&$foo[/color]([COLOR=#008080]$a[/color],[COLOR=#008080]$b[/color]);
[COLOR=#804040][b]print[/b][/color] [COLOR=#ff00ff]"[/color][COLOR=#6a5acd]\$[/color][COLOR=#ff00ff]bar=[/color][COLOR=#008080]$bar[/color][COLOR=#6a5acd]\n[/color][COLOR=#ff00ff]"[/color];

As mentioned above it works only without strict-pragma:

C:\Users\Roman\Work>perl soft_ref.pl
$bar=3
$bar=-1

If you want to use strict-pragma then use hard references.
I would create a hash of references on given functions - something like this:
hard_ref.pl

[COLOR=#0000ff]# Example for using hard refernces[/color]
[COLOR=#0000ff]# works with strict-pragma too[/color]

[COLOR=#804040][b]use strict[/b][/color];
[COLOR=#804040][b]use warnings[/b][/color];

[COLOR=#804040][b]sub[/b][/color][COLOR=#008080] [/color][COLOR=#008080]addition[/color]{
  [COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]$a[/color], [COLOR=#008080]$b[/color]) = [COLOR=#008080]@_[/color];
  [COLOR=#804040][b]return[/b][/color] ([COLOR=#008080]$a[/color]+[COLOR=#008080]$b[/color]);
}

[COLOR=#804040][b]sub[/b][/color][COLOR=#008080] [/color][COLOR=#008080]substraction[/color]{
  [COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]$a[/color], [COLOR=#008080]$b[/color]) = [COLOR=#008080]@_[/color];
  [COLOR=#804040][b]return[/b][/color] ([COLOR=#008080]$a[/color]-[COLOR=#008080]$b[/color]);
}


[COLOR=#804040][b]my[/b][/color] ([COLOR=#008080]%foo_hash[/color], [COLOR=#008080]$operation[/color], [COLOR=#008080]$bar[/color]);

[COLOR=#0000ff]# create hash of function references[/color]
[COLOR=#008080]$foo_hash[/color]{[COLOR=#ff00ff]'[/color][COLOR=#ff00ff]addition[/color][COLOR=#ff00ff]'[/color]} = [COLOR=#008080]\&addition[/color];
[COLOR=#008080]$foo_hash[/color]{[COLOR=#ff00ff]'[/color][COLOR=#ff00ff]substraction[/color][COLOR=#ff00ff]'[/color]} = [COLOR=#008080]\&substraction[/color];

[COLOR=#008080]$a[/color] = [COLOR=#ff00ff]1[/color]; [COLOR=#008080]$b[/color] = [COLOR=#ff00ff]2[/color];
[COLOR=#0000ff]#[/color]
[COLOR=#008080]$operation[/color] = [COLOR=#ff00ff]'[/color][COLOR=#ff00ff]addition[/color][COLOR=#ff00ff]'[/color];
[COLOR=#008080]$bar[/color]=[COLOR=#008080]$foo_hash[/color]{[COLOR=#008080]$operation[/color]}([COLOR=#008080]$a[/color],[COLOR=#008080]$b[/color]);
[COLOR=#804040][b]print[/b][/color] [COLOR=#ff00ff]"[/color][COLOR=#6a5acd]\$[/color][COLOR=#ff00ff]bar=[/color][COLOR=#008080]$bar[/color][COLOR=#6a5acd]\n[/color][COLOR=#ff00ff]"[/color];
[COLOR=#0000ff]#[/color]
[COLOR=#008080]$operation[/color] = [COLOR=#ff00ff]'[/color][COLOR=#ff00ff]substraction[/color][COLOR=#ff00ff]'[/color];
[COLOR=#008080]$bar[/color]=[COLOR=#008080]$foo_hash[/color]{[COLOR=#008080]$operation[/color]}([COLOR=#008080]$a[/color],[COLOR=#008080]$b[/color]);
[COLOR=#804040][b]print[/b][/color] [COLOR=#ff00ff]"[/color][COLOR=#6a5acd]\$[/color][COLOR=#ff00ff]bar=[/color][COLOR=#008080]$bar[/color][COLOR=#6a5acd]\n[/color][COLOR=#ff00ff]"[/color];

C:\Users\Roman\Work>perl hard_ref.pl
$bar=3
$bar=-1

But I wonder why this derefencing simply works

$bar=$foo_hash{$operation}($a,$b);

because IMHO it should be more cryptic - so:

$bar=&{$foo_hash{$operation}}($a,$b);

 

[mikrom]

I forgot to say, that both dereferences work:

$bar=$foo_hash{$operation}($a,$b);

$bar=&{$foo_hash{$operation}}($a,$b);

 

[1DMF]

lol - man I can't even remember taking part.

Amazing how much you forget when you don't use it all the time, but hey it was 4 years ago!

Thanks for finding the old thread and giving me a deserved kick up the behind!

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!"

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