First, whats meant by:

To your comparison: The code sequence (*)

$string='7';
$num=$string+0
[download]

C:\>perl -MO=Concise,-exec -e"$string='7';$num=$string+0"
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <$> const[PV "7"] s
4  <#> gvsv[*string] s
5  <2> sassign vKS/2
6  <;> nextstate(main 1 -e:1) v:{
7  <#> gvsv[*string] s
8  <$> const[IV 0] s
9  <2> add[t4] sK/2
a  <#> gvsv[*num] s
b  <2> sassign vKS/2
c  <@> leave[1 ref] vKP/REFC
[download]

and the sequence (**)

 $string='7';
 $num=int($string)"
[download]

gives (**)

C:\>perl -MO=Concise,-exec -e"$string='7';$num=int($string)"
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <$> const[PV "7"] s
4  <#> gvsv[*string] s
5  <2> sassign vKS/2
6  <;> nextstate(main 1 -e:1) v:{
7  <#> gvsv[*string] s
8  <1> int[t4] sK/1
9  <#> gvsv[*num] s
a  <2> sassign vKS/2
b  <@> leave[1 ref] vKP/REFC
-e syntax OK
[download]

8  <$> const[IV 0] s
9  <2> add[t4] sK/2
[download]

8  <1> int[t4] sK/1
[download]

so there shouldn't be too much difference

Regards

mwa

Thanks!
What I learn from that is: if i am handling non-floating-point values, it's a bit more elegant and possibly a tick faster (one iteration less, 1-b vs 1-c) to use int(), otherwise the +0 trick isn't that much of a hack it seems to be.

if i am handling non-floating-point values, it's a bit more elegant ... to use int()

.. if it's worth the typed characters at all ;-)

As you said before, Perl will convert the string into a number internally if the string isn't already converted (IV-Flag not set) and if the string is used in a numerical context.

Of course, when using Perl-Guts (XS), you have to worry.

regards

mwa

Now, yesterday, I ran into an issue that involved quite low-level transformations and as it turned out (thanks tofjw!), my string value was simply ignored and a *true* numeric value worked.

Now: what is the best way to transform a string to a true numeric value, in terms of speed/internal efficiency?

"Really? If that's true, then there's a bug in Perl."

No need to worry: it was a known bug in an XS module I use here, and the developer of the module already fixed it - but it steered my attention towards this string/number thing.


"You tell us."

Call me a lazy bum, but being the noob that I am at proper benchmarking, I thought a quick post and a question to people who know the Perl internals would be faster.

to people who know the Perl internals

perlmonks ne perl5-porters ;)