Sam Phillips <[EMAIL PROTECTED]> wrote:
> Problem:
> 1) To create an efficient implementation of Basil I'll need a big
> PerlArray that is formed by expressions that create PerlStrings or more
> PerlArrays.
How big is "big"?
> So my main question is this: Are PerlArrays and PerlStrings an efficient
> way to go with this? - how much copying goes on within a string
> concatenation?
There ar basically 2 forms of concat, one inplace and the 2nd creating a
new string. The former is much more efficient the more you are appending
small items to the first string.
> ... Iterator?
Iteration doesn't involve any copying.
> ... etc ( ie does using COW prevent a deep copy
> every time I make a concatenation).
COW doesn't help in the case of concat. COW is mainly useful for
extracting substrings.
> I tried to make sense of PerlString concatenation and they seem to use
> string_concat which in turn has two mem_sys_memcopys doing the actual
> concatenation.
Well, that depends. Inplace needs one only.
> 2) If concat isn't the way forward then push probably is (I could just
> hand back a tree and iterator (as a closure err do I mean continuation?)
> to the calling function). I take it there are no hidden caveats in using
> push on a PerlArray?
Push is fine.
> 3) I take it a proper iterator is far more efficient than a loop with a
> shift in it?
Yep.
> 4) why doesn't '.' work on a PerlString in IMC? :-)
It works - at least partially - inplcace is missing ;)
$ cat c.pir
.sub main
$P0 = new PerlString
$P1 = new PerlString
$P2 = new PerlString
$P0 = "a"
$P1 = "b"
$P2 = $P0 . $P1 # note the space before the dot
print_item $P2
# $P0 .= $P1
# print_item $P0
print_newline
end
.end
$ parrot c.pir
ab
> 5) I guess the way-forward for the future is a custom class of very-lazy
> string-lists that can be concatenated, split, iterated, searched, sorted
> etc
You might have a look at "cord" which can be found e.g. in the gcc sources
under the boehm-gc subdirectory.
> Sambeau
leo
