Re: efficient and safe way to iterate on associative array?
On Friday, 4 March 2016 at 16:46:35 UTC, Steven Schveighoffer
wrote:
You cannot add or remove keys. You can modify values for
existing keys.
Note, in your code, this would not cause a problem, since
setting hash to null just removes the reference from the local
variable 'hash', it does not alter the AA in any way.
In dcollections, all containers support "purging", or iterating
through elements, removing the current element if desired
before moving to the next. But I haven't touched this library
in ages, I don't know if it still compiles even.
-Steve
Thank you for it. Now I know.
I will copy and modify AA source to customize. (src/rt/aaA.d)
I wonder what if D support safe variant like safeByKeyValue.
Actually it seems easy (in aaA.d):
bool _aaRangeEmpty(Range r)
{
return r.impl is null || r.idx == r.dim;
}
can be changed to:
bool _aaRangeEmptySafe(Range r)
{
if(r.impl is null || r.idx >= r.dim) return true;
if (!r.buckets[r.idx].filled) throw xxxException();
return false;
}
It can become safe by a cost of small overhead.
-- Aki.
Re: efficient and safe way to iterate on associative array?
On 3/4/16 8:53 AM, aki wrote:
Is it okay to modify associative array while iterating it?
import std.stdio;
void main() {
string[string] hash = [ "k1":"v1", "k2":"v2" ];
auto r = hash.byKeyValue();
while(!r.empty) {
auto key = r.front.key;
auto value = r.front.value;
r.popFront();
writefln("key=%s, value=%s", key, value);
// may not modify 'hash' here ?
hash = null;
}
}
I guess probably it's not.
Then, my question is are there an efficient and safe way to iterate on
an associative array even if there are possibility to be modified while
iterating?
I'm writing interpreter and want to make my language to be safe; even
malicious script cannot fall it in 'core dump' state. It is okay if it
causes undefined behavior like throw or instant exit from loop, but not
crash.
Thanks, Aki.
You cannot add or remove keys. You can modify values for existing keys.
Note, in your code, this would not cause a problem, since setting hash
to null just removes the reference from the local variable 'hash', it
does not alter the AA in any way.
In dcollections, all containers support "purging", or iterating through
elements, removing the current element if desired before moving to the
next. But I haven't touched this library in ages, I don't know if it
still compiles even.
-Steve
Re: efficient and safe way to iterate on associative array?
On Friday, 4 March 2016 at 13:53:22 UTC, aki wrote:
Is it okay to modify associative array while iterating it?
import std.stdio;
void main() {
string[string] hash = [ "k1":"v1", "k2":"v2" ];
auto r = hash.byKeyValue();
while(!r.empty) {
auto key = r.front.key;
auto value = r.front.value;
r.popFront();
writefln("key=%s, value=%s", key, value);
// may not modify 'hash' here ?
hash = null;
}
}
I guess probably it's not.
Then, my question is are there an efficient and safe way to
iterate on an associative array even if there are possibility
to be modified while iterating?
I'm writing interpreter and want to make my language to be
safe; even malicious script cannot fall it in 'core dump'
state. It is okay if it causes undefined behavior like throw or
instant exit from loop, but not crash.
It is not safe to modify an aa when iterating with .byKey,
.byValue, or .byKeyValue. You can safely do it with .keys and
.values, but these allocate so it isn't likely to be the most
efficient. Your best bet if it's something you need to do
frequently is probably what JR recommended.
Re: efficient and safe way to iterate on associative array?
On Friday, 4 March 2016 at 14:16:55 UTC, Minas Mina wrote: On Friday, 4 March 2016 at 13:53:22 UTC, aki wrote: I think what you can do is extract its contents to an array, iterate it and modify it as you like, and then insert back to another associative array. I don't think it's efficient but I don't know if it's possible to do something else. You can populate an array of key values (here string, so string[]) of the entries to delete, then iterate through it afterwards and call .remove to clean up. http://dpaste.dzfl.pl/b63a8e8e5c3b
Re: efficient and safe way to iterate on associative array?
On Friday, 4 March 2016 at 13:53:22 UTC, aki wrote:
Is it okay to modify associative array while iterating it?
import std.stdio;
void main() {
string[string] hash = [ "k1":"v1", "k2":"v2" ];
auto r = hash.byKeyValue();
while(!r.empty) {
auto key = r.front.key;
auto value = r.front.value;
r.popFront();
writefln("key=%s, value=%s", key, value);
// may not modify 'hash' here ?
hash = null;
}
}
I guess probably it's not.
Then, my question is are there an efficient and safe way to
iterate on an associative array even if there are possibility
to be modified while iterating?
I'm writing interpreter and want to make my language to be
safe; even malicious script cannot fall it in 'core dump'
state. It is okay if it causes undefined behavior like throw or
instant exit from loop, but not crash.
Thanks, Aki.
I think what you can do is extract its contents to an array,
iterate it and modify it as you like, and then insert back to
another associative array. I don't think it's efficient but I
don't know if it's possible to do something else.
efficient and safe way to iterate on associative array?
Is it okay to modify associative array while iterating it?
import std.stdio;
void main() {
string[string] hash = [ "k1":"v1", "k2":"v2" ];
auto r = hash.byKeyValue();
while(!r.empty) {
auto key = r.front.key;
auto value = r.front.value;
r.popFront();
writefln("key=%s, value=%s", key, value);
// may not modify 'hash' here ?
hash = null;
}
}
I guess probably it's not.
Then, my question is are there an efficient and safe way to
iterate on an associative array even if there are possibility to
be modified while iterating?
I'm writing interpreter and want to make my language to be safe;
even malicious script cannot fall it in 'core dump' state. It is
okay if it causes undefined behavior like throw or instant exit
from loop, but not crash.
Thanks, Aki.
