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in reply to Converting a string to a real numeric value - what's faster?

First, whats meant by:

I ran into an issue that involved quite low-level transformations and as it turned out

To your comparison: The code sequence (*)

$string='7';
$num=$string+0

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gives (*): 
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

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and the sequence (**)

 $string='7';
 $num=int($string)"

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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

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The Difference is (*) 
8  <$> const[IV 0] s
9  <2> add[t4] sK/2

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compared to (**) 
8  <1> int[t4] sK/1

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so there shouldn't be too much difference

Regards

mwa

Replies are listed 'Best First'.
Re^2: Converting a string to a real numeric value - what's faster?
by isync (Hermit) on Sep 17, 2009 at 09:50 UTC
    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.
[reply]
      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

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