It seems that all ways to iterate over the characters in a UTF8 string
have quadratic running time. See the attached test. I would expect that
for keyed access and 'substr' but iterator access and 'split' should
have better performance. I had a look at the string iterator PMC code
and it doesn't use the iterators that the underlying string API provides.
I can offer to write a patch to fix this if noone else is working on this.
Nick
.sub _ :main
.local string str
str = utf8:unicode:"ä"
$S0 = repeat "x", 30000
str .= $S0
.local pmc str_pmc
str_pmc = box str
say "iter"
.local pmc i
i = iter str_pmc
iter_loop:
$S0 = shift i
if i goto iter_loop
say "keyed"
$I0 = 0
keyed_loop:
$S0 = str_pmc[$I0]
$I0 += 1
if $S0 != "" goto keyed_loop
say "substr"
$I0 = 0
char_loop:
$S0 = substr str, $I0, 1
$I0 += 1
if $S0 != "" goto char_loop
say "split"
$P0 = split "", str
.end
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