Re^2: Dualvar via table

> I've thought a little about using the dual nature of variables in some perl code, but haven't actually taken the plunge

I'm not sure if it's a good idea. Perl is adjusting the slots to each other depending on use history.

Hence you'd magically loose information, and I'm not aware of a way to inhibit this.

That's awfully hard to debug if it happens.

(will add an example later)

update

Playing around, look at what happens at line 7

  DB<3> use Scalar::Util qw(dualvar);

  DB<4> $v = dualvar 137, 'Buster';

  DB<5> p "$v" 
Buster
  DB<6> p 0+$v
137
  DB<7> p $v++    # read string, increment number
Buster
  DB<8> p $v++    # what...?
138
  DB<9> p "$v"
139
  DB<10>
[download]

after incrementing $v, i.e. changing it in numeric context, the string-slot is adjusted to the number-slot°

So can this only happen when I change one of the slots?

If yes, shouldn't such dualvars always been made readonly, too?

Hope you understand my worries.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery
FootballPerl is like chess, only without the dice}

update

°) or some flags are changed. Who knows....

FWIW: a very good article from Brian here: https://www.effectiveperlprogramming.com/2011/12/create-your-own-dualvars/

Comment on Re^2: Dualvar via table Download Code

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Re^3: Dualvar via table by roboticus (Chancellor) on Jan 18, 2020 at 00:06 UTC
LanX: Yeah, it could be problematic. I haven't put any thought into its ramifications. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re^4: Dualvar via table by LanX (Saint) on Jan 18, 2020 at 00:36 UTC
Regarding your motivation: If I wanted attach extra information to a variable, I'd `bless` its reference. If I wanted to do this with a value, I'd `tie` the info into the value and accessed it via `tied` . Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}	[reply]


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