Re: How to construct a struct that does not explicitly define a constructor
On Saturday, 1 March 2025 at 03:13:55 UTC, user1234 wrote: because the tuple-expression `(0,0.1)` is explicitly convertible to `Test`, based on the concept of "structural typing". Even if D has tuples, I highly doubt that it will have this kind of implicit conversion from tuples to structs. D is generally very conservative about what implicit conversions it allows, especially conversions to and from user-defined types (like structs and classes).
Re: How to construct a struct that does not explicitly define a constructor
On Saturday, 1 March 2025 at 02:19:55 UTC, Meta wrote:
Thanks, I forgot about that syntax. Another question I have is
if there's a way to do this inline:
```d
struct Test
{
int n;
float f;
static Test opCall(int n, float f)
{
//return {n, f};Error
//return Test {n, f}; Error
//return {n: n, f: f}; Error
//return Test {n: n, f: f}; Error
}
}
void main()
{
auto test = Test(1, 2.0);
assert(test.n == 1);
assert(test.f == 2.0);
}
```
As you've been said, that does not work ATM but that is something
that I expect to work from day one when D will have tuples
```d
struct Test
{
int n;
double f;
static Test opCall(int n, float f)
{
return (0,0.1);
}
}
```
because the tuple-expression `(0,0.1)` is explicitly convertible
to `Test`, based on the concept of "structural typing".
Re: How to construct a struct that does not explicitly define a constructor
On Saturday, 1 March 2025 at 02:19:55 UTC, Meta wrote: On Saturday, 1 March 2025 at 00:47:20 UTC, Paul Backus wrote: What you can do is use curly-brace initialization syntax: Thanks, I forgot about that syntax. Another question I have is if there's a way to do this inline: No, there's no way to do it inline. Really, the ideal solution here would be to get rid of your `static opCall` overload (for example, by turning it into a regular `static` method instead).
Re: How to construct a struct that does not explicitly define a constructor
On Saturday, 1 March 2025 at 00:47:20 UTC, Paul Backus wrote:
What you can do is use curly-brace initialization syntax:
```d
struct Test
{
int n;
float f;
static Test opCall(int n, float f)
{
Test result = { n, f };
return result;
}
}
void main()
{
auto test = Test(1, 2.0);
assert(test.n == 1);
assert(test.f == 2.0);
}
```
Thanks, I forgot about that syntax. Another question I have is if
there's a way to do this inline:
```d
struct Test
{
int n;
float f;
static Test opCall(int n, float f)
{
//return {n, f};Error
//return Test {n, f}; Error
//return {n: n, f: f}; Error
//return Test {n: n, f: f}; Error
}
}
void main()
{
auto test = Test(1, 2.0);
assert(test.n == 1);
assert(test.f == 2.0);
}
```
Re: How to construct a struct that does not explicitly define a constructor
On Friday, 28 February 2025 at 23:31:23 UTC, Meta wrote:
```d
struct Test
{
int n;
float f;
static Test opCall(int n, float f)
{
return Test(n, f);
}
}
void main()
{
Test(1, 2.0);
}
```
This code causes an infinite loop because the `Test(n, f)`
inside the static `opCall` is interpreted as a recursive call
to that same `opCall` function - not a call to the struct's
constructor (or however this is interpreted by the compiler
when there is no explicit struct/union constructor defined).
I tried doing `return Test.__ctor(n, f)` but it says that
symbol doesn't exist. Is there any way to explicitly call the
struct's constructor so it doesn't cause an infinitely
recursive call to `opCall`?
You can't call the constructor because there isn't one.
What you can do is use curly-brace initialization syntax:
```d
struct Test
{
int n;
float f;
static Test opCall(int n, float f)
{
Test result = { n, f };
return result;
}
}
void main()
{
auto test = Test(1, 2.0);
assert(test.n == 1);
assert(test.f == 2.0);
}
```
