Re^3: compare arrays numbers

[ikegami]

$a[$_] -= $b[$_] for 0..$#a;

is optimised into a counting loop (O(1) memory).

$a[$_] -= $b[$_] for (),0..$#a;

is not optimised (O(N) memory).

but 0..$#a is a list anyway

".." is usually the range operator, but not in the first example. In fact, it's not an operator at all there. It's just a separator like the semicolons in for(;;).

$ perl -MO=Concise,-exec -e'1 for (),$x..$y'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <;> nextstate(main 1 -e:1) v:{
4  <0> pushmark sM
5  <|> range(other->6)[t3] lK/1      \
6      <#> gvsv[*y] s                 |
7      <1> flop lKM                   | Range op called
           goto 8                     |   to produce a list.
f  <#> gvsv[*x] s                     |
g  <1> flip[t4] lK                   /
8  <#> gv[*_] s
9  <{> enteriter(next->a last->d redo->a) lK/8
b  <0> iter s
c  <|> and(other->a) vK/1
a      <0> unstack v
           goto b
d  <2> leaveloop vK/2
e  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'1 for $x..$y'
1  <0> enter
2  <;> nextstate(main 1 -e:1) v:{
3  <;> nextstate(main 1 -e:1) v:{
4  <0> pushmark s
5  <#> gvsv[*x] s                    \ Args for enteriter/S
6  <#> gvsv[*y] s                    /
7  <#> gv[*_] s
8  <{> enteriter(next->9 last->c redo->9) lKS/8
a  <0> iter s
b  <|> and(other->9) vK/1
9      <0> unstack v
           goto a
c  <2> leaveloop vK/2
d  <@> leave[1 ref] vKP/REFC
-e syntax OK