Re: Using .require for struct types
On Sunday, 11 September 2022 at 21:01:27 UTC, Salih Dincer wrote:
On Saturday, 10 September 2022 at 16:33:03 UTC, Erdem Demir
wrote:
I wish I could use ref DListOfA returnVal = but we can't
in D.
Can you please suggest alternatives?
I think you should try advanced update. Your flexibility and
what you can do are limited by your dreams. A couple delicious
code:
```d
import object, std.container;
struct A
{
double val;
bool isBig;
}
void main()
{
alias DListOfA = DList!A;
DListOfA returnVal;
//DListOfA[string] temp;/*
DListOfA[string] temp = [
"a": DListOfA( A(0) )
];//*/
auto a = A(6, true); // replacement element
temp.update("a", {
return DListOfA( A(0) ); // not updated: unsucceeded
but initialized
}, (ref DListOfA v) {
v = DListOfA( a ); // existing v has been replaced
returnVal = v;
assert(returnVal.front == a);
});
assert(is(typeof(temp["a"]) == DList!A));
}
```
SDB@79
I really like the possibilities of update as well but the
overhead is too much especially in this example. I am sorry to
say I found old "in" usage less complicated than that even I
think "in" is complicated. I liked the Steven's solution all this
code can be done via 2 lines only.
Re: Using .require for struct types
On Saturday, 10 September 2022 at 18:39:55 UTC, Steven Schveighoffer wrote: On 9/10/22 12:33 PM, Erdem Demir wrote: Can you please suggest alternatives? Use a pointer. ```d DListOfA *returnVal = (...); returnVal.insert(a); ``` -Steve Actually that could be answer I am seeking for I will try it.
Re: Using .require for struct types
On Saturday, 10 September 2022 at 18:38:40 UTC, Ali Çehreli wrote:
On 9/10/22 09:33, Erdem Demir wrote:
> DListOfA returnVal = temp.require("a",
DListOfA());--> I wish I
> could use ref DListOfA here
But keeping a reference to a temporary would not work because
the life of that temporary ends by the end of that expression
(practically, at the semicolon).
An option is to allocate the object dynamically with new (and
store DListOfA* in the associative array). Then the GC would
keep it alive as long its pointer was in the associative arrray.
But a better option is to just forget about it because D
already takes care of rvalues by blitting (bit-level copying)
them by default. Everything just works... :) It is not
expensive either. For example, your struct is very cheap to
copy.
But I am probably missing the reason why you want a ref there.
Perhaps there are even better options.
Ali
In the code sample I posted I need returnVal.insert(a); have an
effect on DListOfA[string] temp; but if returnVal is a rvalue
copy I can't accomplish this right?
I see your point about ref would have been assign to a temp val,
thanks for pointing out.
Re: Using .require for struct types
On Saturday, 10 September 2022 at 16:33:03 UTC, Erdem Demir wrote:
I wish I could use ref DListOfA returnVal = but we can't
in D.
Can you please suggest alternatives?
I think you should try advanced update. Your flexibility and what
you can do are limited by your dreams. A couple delicious code:
```d
import object, std.container;
struct A
{
double val;
bool isBig;
}
void main()
{
alias DListOfA = DList!A;
DListOfA returnVal;
//DListOfA[string] temp;/*
DListOfA[string] temp = [
"a": DListOfA( A(0) )
];//*/
auto a = A(6, true); // replacement element
temp.update("a", {
return DListOfA( A(0) ); // not updated: unsucceeded but
initialized
}, (ref DListOfA v) {
v = DListOfA( a ); // existing v has been replaced
returnVal = v;
assert(returnVal.front == a);
});
assert(is(typeof(temp["a"]) == DList!A));
}
```
SDB@79
Re: Using .require for struct types
On 9/10/22 09:33, Erdem Demir wrote:
> DListOfA returnVal = temp.require("a", DListOfA());--> I wish I
> could use ref DListOfA here
But keeping a reference to a temporary would not work because the life
of that temporary ends by the end of that expression (practically, at
the semicolon).
An option is to allocate the object dynamically with new (and store
DListOfA* in the associative array). Then the GC would keep it alive as
long its pointer was in the associative arrray.
But a better option is to just forget about it because D already takes
care of rvalues by blitting (bit-level copying) them by default.
Everything just works... :) It is not expensive either. For example,
your struct is very cheap to copy.
But I am probably missing the reason why you want a ref there. Perhaps
there are even better options.
Ali
Re: Using .require for struct types
On 9/10/22 12:33 PM, Erdem Demir wrote: Can you please suggest alternatives? Use a pointer. ```d DListOfA *returnVal = (...); returnVal.insert(a); ``` -Steve
