Re: How can I match every instance of a template type (struct)?
On Tuesday, 12 July 2022 at 13:34:42 UTC, rempas wrote: [...] Thank you all for your help! @Ali Çehreli That makes things much much easier! I'll look at the source code in "traits.d" and I'll copy-paste it into my library ;)
Re: How can I match every instance of a template type (struct)?
On Tuesday, 12 July 2022 at 15:30:03 UTC, Ali Çehreli wrote:
An alternative:
https://dlang.org/phobos/std_traits.html#isInstanceOf
This is a really good alternative. Because I used to have to
write longer. Thanks, the LOG thing is better now:
```d
struct LOG(T...) {
T[0] id;
T[1] data;
}
void main()
{
auto obj = //make_test(20);/*
make_test('T');//*/
alias typ = //typeof(obj);/*
LOG!(int, char);//*/
"Type: ".write;
if(isInstanceOf!(LOG, typ)/*
is(typ : Template!Args,
alias Template, Args...)//*/
) "LOG".writeln;
}
```
SDB@79
Re: How can I match every instance of a template type (struct)?
On 7/12/22 06:34, rempas wrote:
>static if (is(typeof(obj) == Test)) { printf("YES!!!\n"); }
An alternative:
import std.traits;
static if (isInstanceOf!(Test, typeof(obj))) { printf("YES!!!\n"); }
https://dlang.org/phobos/std_traits.html#isInstanceOf
Ali
Re: How can I match every instance of a template type (struct)?
On Tuesday, 12 July 2022 at 13:56:11 UTC, rempas wrote:
On Tuesday, 12 July 2022 at 13:37:49 UTC, ag0aep6g wrote:
static if (is(typeof(obj) == Test!T, T)) {
printf("YES!!!\n"); }
Haah? Ok, what does this work anyway? I thought you needed
parenthesis for more than 1 templated arguments...
The second `T` is not a template argument. It's an operand of the
"IsExpression".
You can read more about those expressions here:
https://dlang.org/spec/expression.html#is-parameter-list
Re: How can I match every instance of a template type (struct)?
On Tue, Jul 12, 2022 at 01:56:11PM +, rempas via Digitalmars-d-learn wrote:
> On Tuesday, 12 July 2022 at 13:37:49 UTC, ag0aep6g wrote:
> >
> > static if (is(typeof(obj) == Test!T, T)) { printf("YES!!!\n"); }
>
> Haah? Ok, what does this work anyway? I thought you needed
> parenthesis for more than 1 templated arguments...
If your template has multiple parameters, just write:
static if (is(typeof(obj) == Test!Args, Args...)) ...
T
--
Don't drink and derive. Alcohol and algebra don't mix.
Re: How can I match every instance of a template type (struct)?
On Tuesday, 12 July 2022 at 13:37:49 UTC, ag0aep6g wrote:
static if (is(typeof(obj) == Test!T, T)) {
printf("YES!!!\n"); }
Haah? Ok, what does this work anyway? I thought you needed
parenthesis for more than 1 templated arguments...
Re: How can I match every instance of a template type (struct)?
On 12.07.22 15:34, rempas wrote:
extern (C) void main() {
auto obj = make_test(20);
static if (is(typeof(obj) == Test)) { printf("YES!!!\n"); }
}
static if (is(typeof(obj) == Test!T, T)) { printf("YES!!!\n"); }
How can I match every instance of a template type (struct)?
I want to do something like the following:
```d
import core.stdc.stdio;
Test!(T, "mode1") make_test(T)(T data) {
Test!(T, "mode1") t = { data };
return t;
}
struct Test(T, string mode = "ref") { T data; }
extern (C) void main() {
auto obj = make_test(20);
static if (is(typeof(obj) == Test)) { printf("YES!!!\n"); }
}
```
So, I just want to be able check if a variable is a given struct
type. I also want to be able to do something similar but having a
(templated) function that returns a struct type without having to
be limited to a specific initialization of it.
Obviously, the given code will not work. It will result to the
following error message:
```
Error: template struct `test.Test(T, string mode = "ref")` is
used as a type without instantiation; to instantiate it use
`Test!(arguments)`
```
Any ideas? Also, like in every question I make, the solution must
be "betterC" compatible.
**CLARIFICATION**
I have a bad feeling that the post is not clear enough, so I'll
save us all some time by making it clear.
I know I can do this:
```d
static if (is(typeof(obj) == Test!(int, "mode1"))) {
printf("YES!!!\n"); }
```
And it will work but this is not what I want. I want to much
EVERY "Test" type regardless of what's the value
of its templated arguments.
