anyway I think it's a notable result of this discussion that the location of constants and literals will not be fixed at compiletime!

That's not true. Constants are allocated once at compile time.

for (1..3) {
   print(\1, "\n");

   push @x, 'x';  # Prevent reuse of memory addresses.
}
[download]

SCALAR(0x236d94)
SCALAR(0x236d94)
SCALAR(0x236d94)
[download]

They are tied to the opcode, and the same constant is returned every time.

PP(pp_const)
{
    dVAR;
    dSP;
    XPUSHs(cSVOP_sv);
    RETURN;
}
[download]

If you see otherwise, it's because you're looking at a *copy* of the constant.

Note that different instances of the same literal results in different constants.

for (1..3) {
   print(\1, ' ', \1, "\n");

   push @x, 'x';  # Prevent reuse of memory addresses.
}
[download]

SCALAR(0x236d94) SCALAR(0x183179c)
SCALAR(0x236d94) SCALAR(0x183179c)
SCALAR(0x236d94) SCALAR(0x183179c)
[download]

I have to admit, I don't understand your code, I know \1 in the context of RegEx but otherwise couldn't find any reference for it in the docs. do you have a link, please?

please explain
> If you see otherwise, it's because you're looking at a *copy* of the constant.

$_[0] is supossed to be an alias to the parameter

  
DB<1> sub pr { print \$_[0] }
DB<2> $a="x"
DB<3> print \$a
SCALAR(0x852b11c)
DB<4> pr $a
SCALAR(0x852b11c)
[download]

Or do you mean that aliased symbols of variables in perl don't neccessarily have the same reference?

I suppose this can possibly be done with typeglogs ... do mean this or a similar mechanism?

Cheers Rolf

I have to admit, I don't understand your code, I know \1 in the context of RegEx but otherwise couldn't find any reference for it in the docs. do you have a link, please?

1 is a constant. \ takes a reference.

Or do you mean that aliased symbols of variables in perl don't neccessarily have the same reference?

I didn't speculate or investigate what a copy would be made.

However, I made a mistake. I forgot to take into account that \1 is a constant itself.

>perl -MO=Concise -e"$x = \1"
6  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
5     <2> sassign vKS/2 ->6
3        <$> const[RV \1] s ->4             <-----
-        <1> ex-rv2sv sKRM*/1 ->5
4           <#> gvsv[*x] s ->5
-e syntax OK
[download]

My conclusion was based on observed results, which were based on a faulty assumption. Please ignore.

On the plus side, it's a simple of way of generating a unique id for a spot in a file! Isn't that what you were after? It's not clear how you'd find out which spot is associated with which id, though.