Re: How to use a char[] buffer in D
On Thu, Jun 23, 2016 at 08:36:57AM -0700, H. S. Teoh via Digitalmars-d-learn
wrote:
> On Thu, Jun 23, 2016 at 10:00:33AM -0400, Steven Schveighoffer via
> Digitalmars-d-learn wrote:
[...]
> > > On Wednesday, 22 June 2016 at 22:41:24 UTC, H. S. Teoh wrote:
[...]
> > > > Maybe try:
> > > >
> > > > if (buffer[] in myHash) { ... }
> > > >
> > > > ? Does that make a difference?
> > > >
> > > >
> > > > T
> > >
> > >
> >
> > This seems like a bug in the runtime, or am I missing something?
> [...]
>
> It might well be a bug. I'll take a look.
[...]
It is indeed a bug. It's caused by the AA implementation receiving a
static char array when it's expecting a string (immutable(char)[])
according to the declared key type of the AA.
Filed a bug for this:
https://issues.dlang.org/show_bug.cgi?id=16199
The compiler should either reject indexing an AA with a char[n], or it
should automatically slice the char[n] so that the AA implementation
gets the correct type in the key argument.
T
--
Those who don't understand D are condemned to reinvent it, poorly. -- Daniel N
Re: How to use a char[] buffer in D
On Thu, Jun 23, 2016 at 10:00:33AM -0400, Steven Schveighoffer via
Digitalmars-d-learn wrote:
> On 6/23/16 1:59 AM, Andrew Chapman wrote:
> > Perfect, thank you! :-) Works like a charm.
> >
> > On Wednesday, 22 June 2016 at 22:41:24 UTC, H. S. Teoh wrote:
> > > On Wed, Jun 22, 2016 at 09:57:04PM +, Andrew Chapman via
> > > Digitalmars-d-learn wrote:
> >
> > > Maybe try:
> > >
> > > if (buffer[] in myHash) { ... }
> > >
> > > ? Does that make a difference?
> > >
> > >
> > > T
> >
> >
>
> This seems like a bug in the runtime, or am I missing something?
[...]
It might well be a bug. I'll take a look.
T
--
Genius may have its limitations, but stupidity is not thus handicapped. --
Elbert Hubbard
Re: How to use a char[] buffer in D
On 6/23/16 1:59 AM, Andrew Chapman wrote:
Perfect, thank you! :-) Works like a charm.
On Wednesday, 22 June 2016 at 22:41:24 UTC, H. S. Teoh wrote:
On Wed, Jun 22, 2016 at 09:57:04PM +, Andrew Chapman via
Digitalmars-d-learn wrote:
Maybe try:
if (buffer[] in myHash) { ... }
? Does that make a difference?
T
This seems like a bug in the runtime, or am I missing something?
-Steve
Re: How to use a char[] buffer in D
On Thursday, 23 June 2016 at 05:59:10 UTC, Andrew Chapman wrote:
Perfect, thank you! :-) Works like a charm.
On Wednesday, 22 June 2016 at 22:41:24 UTC, H. S. Teoh wrote:
On Wed, Jun 22, 2016 at 09:57:04PM +, Andrew Chapman via
Digitalmars-d-learn wrote:
Maybe try:
if (buffer[] in myHash) { ... }
? Does that make a difference?
T
If the keys are fixed-length, you may want to consider using
immutable(char[4]) as key. That way there is no GC allocation for
the strings at all, the only allocations are done by the AA.
Re: How to use a char[] buffer in D
Perfect, thank you! :-) Works like a charm.
On Wednesday, 22 June 2016 at 22:41:24 UTC, H. S. Teoh wrote:
On Wed, Jun 22, 2016 at 09:57:04PM +, Andrew Chapman via
Digitalmars-d-learn wrote:
Maybe try:
if (buffer[] in myHash) { ... }
? Does that make a difference?
T
Re: How to use a char[] buffer in D
On Wed, Jun 22, 2016 at 09:57:04PM +, Andrew Chapman via
Digitalmars-d-learn wrote:
> Hi everyone, just wanting some help with optimisation if anyone is
> kind enough :-)
>
> I have a loop that iterates potentially millions of times, and inside
> that loop I have code that appends some strings together, e.g.:
>
> string key = s1 ~ "_" ~ s2;
>
> I discovered that due to the memory allocation required, this slows
> the execution significantly.
>
> s1 is always a two character string, e.g "AA", and s2 is always a
> single character.
Yes, frequent allocation of small strings is a performance killer. Using
a static array (as you've done below) is much better.
> What I want to do is something like this:
>
> Outside the loop:
>
> char[4] buffer;
> buffer[2] = '_';
>
> Then inside the loop
>
> buffer[0] = s1[0];
> buffer[1] = s1[1];
> buffer[3] = s2[0];
>
> This works OK, however, I then need to use the buffer value to check
> for an existing value in a hashmap / associative array.
>
> Code such as:
>
> if(buffer in myHash) {
>
> }
>
> throws an access violation. A string value works without error. Is
> there a way for me to use a buffer AND use it in functions expecting
> strings?
Maybe try:
if (buffer[] in myHash) { ... }
? Does that make a difference?
T
--
This sentence is false.
Re: How to use a char[] buffer in D
On 06/22/2016 02:57 PM, Andrew Chapman wrote:
> Code such as:
>
> if(buffer in myHash) {
>
> }
>
> throws an access violation. A string value works without error.
Does it throw an exception? Can you reproduce the issue with a short
program?
Ali
How to use a char[] buffer in D
Hi everyone, just wanting some help with optimisation if anyone
is kind enough :-)
I have a loop that iterates potentially millions of times, and
inside that loop I have code that appends some strings together,
e.g.:
string key = s1 ~ "_" ~ s2;
I discovered that due to the memory allocation required, this
slows the execution significantly.
s1 is always a two character string, e.g "AA", and s2 is always a
single character.
What I want to do is something like this:
Outside the loop:
char[4] buffer;
buffer[2] = '_';
Then inside the loop
buffer[0] = s1[0];
buffer[1] = s1[1];
buffer[3] = s2[0];
This works OK, however, I then need to use the buffer value to
check for an existing value in a hashmap / associative array.
Code such as:
if(buffer in myHash) {
}
throws an access violation. A string value works without error.
Is there a way for me to use a buffer AND use it in functions
expecting strings?
I can use idup() on the char[] to make a string, but again we're
allocating memory which I'd rather avoid.
Thanks sincerely in advance,
Cheers,
Andrew.
