Re: What is a sink delegate?
On Friday, 10 October 2014 at 04:42:04 UTC, thedeemon wrote:
On Friday, 10 October 2014 at 03:06:33 UTC, Joel wrote:
How do you use that toString? Maybe an example?
void main() {
Try t = Try(Joel, 35);
t.toString(s = writeln(s));
}
I think that the problem pointed by the OP is that toString is
usually used automatically for struct in std.conv when it's
implemented. I'm myself quite dubitatif in front of this syntax,
even if IIRC during one talk of the DConf 2014 someone claim
that's it's faster.
Re: What is a sink delegate?
On 10/10/14 1:00 AM, Ali Çehreli wrote:
On 10/09/2014 08:06 PM, Joel wrote:
On Tuesday, 30 September 2014 at 17:27:09 UTC, Adam D. Ruppe wrote:
On Tuesday, 30 September 2014 at 17:22:44 UTC, Gary Willoughby wrote:
What is a sink delegate?
Instead of
string toString() { return foo; }
for example, you would use:
void toString(void delegate(string) sink) { sink(foo); }
The sink argument there is then free to view and discard the data or
to make a private copy using whatever scheme it desires.
How do you use that toString? Maybe an example? Below is my failed
effort.
import std.stdio;
struct Try {
string name;
long age;
void toString(void delegate(string) sink) {
sink(foo);
}
}
void main() {
Try t = Try(Joel, 35);
writeln(t);
}
The signature of that toString is different from what I have been seeing
and using. The following works:
void toString(void delegate(const(char)[]) sink) const {
The delegate parameter is what is important. The function that is going
to be passed in takes a const(char)[], which actually should, but does
not, implicitly cast to a delegate(string) (see issue
https://issues.dlang.org/show_bug.cgi?id=3075).
The const outside is irrelevant to whether it will accept it or not,
that is a contract between the toString function and your object. If you
want a non-const toString, I think that should work.
(actually, testing it...) Yep, it works without the const on the outside.
-Steve
Re: What is a sink delegate?
On 10/10/2014 06:30 AM, Steven Schveighoffer wrote:
On 10/10/14 1:00 AM, Ali Çehreli wrote:
On 10/09/2014 08:06 PM, Joel wrote:
On Tuesday, 30 September 2014 at 17:27:09 UTC, Adam D. Ruppe wrote:
On Tuesday, 30 September 2014 at 17:22:44 UTC, Gary Willoughby wrote:
What is a sink delegate?
Instead of
string toString() { return foo; }
for example, you would use:
void toString(void delegate(string) sink) { sink(foo); }
The sink argument there is then free to view and discard the data or
to make a private copy using whatever scheme it desires.
How do you use that toString? Maybe an example? Below is my failed
effort.
import std.stdio;
struct Try {
string name;
long age;
void toString(void delegate(string) sink) {
sink(foo);
}
}
void main() {
Try t = Try(Joel, 35);
writeln(t);
}
The signature of that toString is different from what I have been seeing
and using. The following works:
void toString(void delegate(const(char)[]) sink) const {
The delegate parameter is what is important. The function that is going
to be passed in takes a const(char)[],
That is what I meant.
which actually should, but does
not, implicitly cast to a delegate(string) (see issue
https://issues.dlang.org/show_bug.cgi?id=3075).
The const outside is irrelevant to whether it will accept it or not,
that is a contract between the toString function and your object. If you
want a non-const toString, I think that should work.
(actually, testing it...) Yep, it works without the const on the outside.
But not for const objects. The following program does not call the user
defined toString:
import std.stdio;
import std.conv;
struct S
{
int i;
void toString(void delegate(const(char)[]) sink)
{
sink(i.to!string);
}
}
void main()
{
const c = S(42);
writeln(c);
}
Add a const at the end, now it calls the user defined one.
-Steve
Ali
Re: What is a sink delegate?
On 10/10/14 11:20 AM, Ali Çehreli wrote:
On 10/10/2014 06:30 AM, Steven Schveighoffer wrote:
The const outside is irrelevant to whether it will accept it or not,
that is a contract between the toString function and your object. If you
want a non-const toString, I think that should work.
(actually, testing it...) Yep, it works without the const on the
outside.
But not for const objects.
I think that's what I said :) It's a contract between the toString
function and your object, it has nothing to do with writeln accepting
the function. There are some quirky requirements for certain magic
functions in phobos that have to be exactly a certain signature for the
compiler to use it.
Now, obviously, the toy example can be labeled const. But not one that
might, say, cache some state in order to compute the output.
The following program does not call the user
defined toString:
import std.stdio;
import std.conv;
struct S
{
int i;
void toString(void delegate(const(char)[]) sink)
{
sink(i.to!string);
Don't do this. Do this instead:
import std.format;
sink.formattedWrite(i);
The former allocates memory on the heap, just to throw it away. You are
completely losing the benefit of the sink.
-Steve
Re: What is a sink delegate?
On Friday, 10 October 2014 at 11:35:21 UTC, Hjkp wrote:
On Friday, 10 October 2014 at 04:42:04 UTC, thedeemon wrote:
On Friday, 10 October 2014 at 03:06:33 UTC, Joel wrote:
How do you use that toString? Maybe an example?
void main() {
Try t = Try(Joel, 35);
t.toString(s = writeln(s));
}
I think that the problem pointed by the OP is that toString is
usually used automatically for struct in std.conv when it's
implemented. I'm myself quite dubitatif in front of this
syntax, even if IIRC during one talk of the DConf 2014 someone
claim that's it's faster.
I think it was in
http://dconf.org/2014/talks/strasuns.html
Re: What is a sink delegate?
Thanks thedeemon.
On Friday, 10 October 2014 at 04:42:04 UTC, thedeemon wrote:
On Friday, 10 October 2014 at 03:06:33 UTC, Joel wrote:
How do you use that toString? Maybe an example?
void main() {
Try t = Try(Joel, 35);
t.toString(s = writeln(s));
}
Re: What is a sink delegate?
On Tuesday, 30 September 2014 at 17:27:09 UTC, Adam D. Ruppe
wrote:
On Tuesday, 30 September 2014 at 17:22:44 UTC, Gary Willoughby
wrote:
What is a sink delegate?
Instead of
string toString() { return foo; }
for example, you would use:
void toString(void delegate(string) sink) { sink(foo); }
The sink argument there is then free to view and discard the
data or to make a private copy using whatever scheme it desires.
How do you use that toString? Maybe an example? Below is my
failed effort.
import std.stdio;
struct Try {
string name;
long age;
void toString(void delegate(string) sink) {
sink(foo);
}
}
void main() {
Try t = Try(Joel, 35);
writeln(t);
}
Re: What is a sink delegate?
On Friday, 10 October 2014 at 03:06:33 UTC, Joel wrote:
How do you use that toString? Maybe an example?
void main() {
Try t = Try(Joel, 35);
t.toString(s = writeln(s));
}
Re: What is a sink delegate?
On 10/09/2014 08:06 PM, Joel wrote:
On Tuesday, 30 September 2014 at 17:27:09 UTC, Adam D. Ruppe wrote:
On Tuesday, 30 September 2014 at 17:22:44 UTC, Gary Willoughby wrote:
What is a sink delegate?
Instead of
string toString() { return foo; }
for example, you would use:
void toString(void delegate(string) sink) { sink(foo); }
The sink argument there is then free to view and discard the data or
to make a private copy using whatever scheme it desires.
How do you use that toString? Maybe an example? Below is my failed effort.
import std.stdio;
struct Try {
string name;
long age;
void toString(void delegate(string) sink) {
sink(foo);
}
}
void main() {
Try t = Try(Joel, 35);
writeln(t);
}
The signature of that toString is different from what I have been seeing
and using. The following works:
void toString(void delegate(const(char)[]) sink) const {
Ali
What is a sink delegate?
What is a sink delegate? Discussed here: http://forum.dlang.org/thread/m0bdgg$1t7j$1...@digitalmars.com?page=6#post-m0emvc:242av5:241:40digitalmars.com
Re: What is a sink delegate?
On Tuesday, 30 September 2014 at 17:22:44 UTC, Gary Willoughby
wrote:
What is a sink delegate?
Instead of
string toString() { return foo; }
for example, you would use:
void toString(void delegate(string) sink) { sink(foo); }
The sink argument there is then free to view and discard the data
or to make a private copy using whatever scheme it desires.
Re: What is a sink delegate?
On 9/30/14 1:22 PM, Gary Willoughby wrote: What is a sink delegate? Discussed here: http://forum.dlang.org/thread/m0bdgg$1t7j$1...@digitalmars.com?page=6#post-m0emvc:242av5:241:40digitalmars.com Aside from Adam's answer, the term 'sink' means to draw out something, as in 'heat sink'. So basically a sink delegate is a place to put the string data. -Steve
