And then there's 1..100_000 that creates an array and 100,000 scalars at compile-time.

It does? How can you tell?

Neither B::Deparse nor B::Concise seem to indicate that, nor the compile time memory consumption.

It shows up as const AV in the opcode tree.

You can prove the list is flattened once using

for (1..2) {
   for ((), 4..8) {
      say $_++;
   }
}
[download]

Update: Added missing parens.

But the 100k scalars don't show up in the optree. Where are they?

Perl 6 - second systems done right

It shows up as const AV in the opcode tree.

You can prove the list is flattened once using

I see the 1 & 2, and 4 & 8 as consts, but I'm also seeing what look to me like two loops. Perhaps you can interpret it better?:

c:\test>perl -MO=Concise
for (1..2) {
    for (4..8) {
       say $_++;
    }
 }
^Z
t  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 4 -:1) v:{ ->3
s     <2> leaveloop vK/2 ->t
7        <{> enteriter(next->p last->s redo->8) lKS/8 ->q
-           <0> ex-pushmark s ->3
-           <1> ex-list lK ->6
3              <0> pushmark s ->4
4              <$> const[IV 1] s ->5
5              <$> const[IV 2] s ->6
6           <#> gv[*_] s ->7
-        <1> null vK/1 ->s
r           <|> and(other->8) vK/1 ->s
q              <0> iter s ->r
-              <@> lineseq vKP ->-
8                 <;> nextstate(main 2 -:2) v:{ ->9
o                 <2> leaveloop vK/2 ->p
d                    <{> enteriter(next->l last->o redo->e) lKS/8 ->m
-                       <0> ex-pushmark s ->9
-                       <1> ex-list lK ->c
9                          <0> pushmark s ->a
a                          <$> const[IV 4] s ->b
b                          <$> const[IV 8] s ->c
c                       <#> gv[*_] s ->d
-                    <1> null vK/1 ->o
n                       <|> and(other->e) vK/1 ->o
m                          <0> iter s ->n
-                          <@> lineseq vKP ->-
e                             <;> nextstate(main 1 -:3) v:{ ->f
k                             <1> preinc[t7] vK/1 ->l
j                                <1> entersub[t6] sKRMS/NO(),TARG ->k
f                                   <0> pushmark s ->g
-                                   <1> ex-rv2sv sKM/1 ->h
g                                      <#> gvsv[*_] s ->h
h                                   <$> method_named[PV "say"] s ->i
i                                   <1> rv2cv /NO() ->j
l                             <0> unstack v ->m
p                 <0> unstack v ->q
- syntax OK
[download]

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

And then there's 1..100_000 that creates an array and 100,000 scalars at compile-time.

Really? Can you demonstrate that?

Because I see no evidence for it:

c:\test>perl -le"++$n for 1..1e2; system qq[tasklist /nh /fi \"pid eq 
+$$\"] "

perl.exe                      7500 Console                    1      5
+,716 K

c:\test>perl -le"++$n for 1..1e3; system qq[tasklist /nh /fi \"pid eq 
+$$\"] "

perl.exe                      3676 Console                    1      5
+,712 K

c:\test>perl -le"++$n for 1..1e4; system qq[tasklist /nh /fi \"pid eq 
+$$\"] "

perl.exe                      6048 Console                    1      5
+,732 K

c:\test>perl -le"++$n for 1..1e5; system qq[tasklist /nh /fi \"pid eq 
+$$\"] "

perl.exe                      5648 Console                    1      5
+,720 K

c:\test>perl -le"++$n for 1..1e6; system qq[tasklist /nh /fi \"pid eq 
+$$\"] "

perl.exe                      8620 Console                    1      5
+,736 K
[download]

Whilst the memory usage varies a little, it sometime goes down a few k when the notional size of this array increases by an order of magnitude?

Conversely, if you explicitly create an array of that size, the memory requirement increases by 100MB as expected:

c:\test>perl -le"@a = 1 .. 1e6; system qq[tasklist /nh /fi \"pid eq $$
+\"] "

perl.exe                      2664 Console                    1    109
+,576 K
[download]

> Because I see no evidence for it:

Not surprising

for (START .. STOP) { }

is magically optimized into an iterator to avoid building the list.

But if you try

for (reverse START .. STOP) { }

instead, you will see the memory consumption, because that optimization is (unfortunately) missing here.

Cheers Rolf