Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

Re^2: Dualvars besides $! (boring)

by tye (Cardinal)
on Jan 28, 2014 at 02:16 UTC ( #1072308=note: print w/ replies, xml ) Need Help??


in reply to Re: Dualvars besides $!
in thread Dualvars besides $!

IMHO, that's a rather stupid interpretation of "dualvar". If the string value equals the stringification of the other value (IV or NV), then it shouldn't be considered a "dualvar". But then, that's what one would expect from a lazy XS function. A Perl version would just do 0+$x eq $x instead.

!1 doesn't need to be implemented as a dualvar. $x=''; {no warnings; 0+$x;} is also enough to get you what is needed for !1 (a string value of '' and a numeric value of 0 w/o a warning). The canonical value for !1 that Perl uses happens to be a real dualvar, though. But "both an empty string and zero" isn't enough to imply "dualvar".

Win32::TieRegistry can use dualvars.

Update: To be clearer, a Perl version of isdual() would be:

sub isdual { my( $v ) = @_; no warnings; return 0 if int $v ne $v^'0' # No IV nor NV in value || $v eq 0+$v # Cached string just same as IV/NV || $v == "$v" # Cached number just same as 0+PV ; return 1; }

- tye        


Comment on Re^2: Dualvars besides $! (boring)
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1072308]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others romping around the Monastery: (19)
As of 2015-07-29 14:02 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (263 votes), past polls