Re: importing std.array: empty in a struct messes things up
On Sunday, 4 March 2018 at 20:07:06 UTC, visitor wrote:
On Sunday, 4 March 2018 at 19:53:59 UTC, ag0aep6g wrote:
On 03/04/2018 08:45 PM, ag0aep6g wrote:
I don't know what's going on here. The error message doesn't
make sense to me. Might be a bug in the compiler.
This one works:
struct Stack(T) {
T[] stack;
alias stack this;
bool empty() {return empty(stack);} /* not using UFCS */
import std.array: empty; /* has to come after the method */
}
Looks very much like a compiler bug now. As far as I know, the
order of declarations shouldn't have an effect like that in
structs. And UFCS should also be ok there, as far as I can
tell.
?
https://run.dlang.io/is/Ws0qEx
https://run.dlang.io/is/Bancgx
struct Stack(T) {
import std.array: empty;
T[] stack;
alias stack this;
bool empty() { return empty(stack); }
}
void main()
{
Stack!int stack;
//bool x = stack.empty; // fails
bool x = stack.empty(); // works
}
Re: importing std.array: empty in a struct messes things up
On Sunday, 4 March 2018 at 19:53:59 UTC, ag0aep6g wrote:
On 03/04/2018 08:45 PM, ag0aep6g wrote:
I don't know what's going on here. The error message doesn't
make sense to me. Might be a bug in the compiler.
This one works:
struct Stack(T) {
T[] stack;
alias stack this;
bool empty() {return empty(stack);} /* not using UFCS */
import std.array: empty; /* has to come after the method */
}
Looks very much like a compiler bug now. As far as I know, the
order of declarations shouldn't have an effect like that in
structs. And UFCS should also be ok there, as far as I can tell.
?
https://run.dlang.io/is/Ws0qEx
https://run.dlang.io/is/Bancgx
Re: importing std.array: empty in a struct messes things up
I had the same issue, happens with any conflicting selective import. It seems to work if you dont use selective imports, but importing it inside the function if possible is a better option.
Re: importing std.array: empty in a struct messes things up
On 03/04/2018 08:45 PM, ag0aep6g wrote:
I don't know what's going on here. The error message doesn't make sense
to me. Might be a bug in the compiler.
This one works:
struct Stack(T) {
T[] stack;
alias stack this;
bool empty() {return empty(stack);} /* not using UFCS */
import std.array: empty; /* has to come after the method */
}
Looks very much like a compiler bug now. As far as I know, the order of
declarations shouldn't have an effect like that in structs. And UFCS
should also be ok there, as far as I can tell.
Re: importing std.array: empty in a struct messes things up
On 03/04/2018 08:17 PM, Dennis wrote:
I was making a stack interface for an array:
```
struct Stack(T) {
import std.array: empty;
T[] stack;
alias stack this;
}
void main()
{
Stack!int stack;
bool x = stack.empty;
}
```
My expectation is that you can now call `empty` on a stack instance
since I imported it in the struct, but it gives this error:
```
Error: cannot resolve type for stack.empty(T)(auto ref scope const(T) a)
if (is(typeof(a.length) : size_t) || isNarrowString!T)
```
`stack.empty` is an alias of `std.array.empty`. It's not a method of the
struct. It's not a UFCS call to `std.array.empty`.
You can call it this way: `stack.empty(stack)`. You can also call it
this way: `Stack!int.empty(stack)`. Maybe that makes it more obvious
what's going on.
When adding this method to the struct:
```
bool empty() {return stack.empty;}
```
I get this confusing error:
```
Error: expression stack.empty is void and has no value
```
I don't know what's going on here. The error message doesn't make sense
to me. Might be a bug in the compiler.
importing std.array: empty in a struct messes things up
I was making a stack interface for an array:
```
struct Stack(T) {
import std.array: empty;
T[] stack;
alias stack this;
}
void main()
{
Stack!int stack;
bool x = stack.empty;
}
```
My expectation is that you can now call `empty` on a stack
instance since I imported it in the struct, but it gives this
error:
```
Error: cannot resolve type for stack.empty(T)(auto ref scope
const(T) a) if (is(typeof(a.length) : size_t) || isNarrowString!T)
```
When adding this method to the struct:
```
bool empty() {return stack.empty;}
```
I get this confusing error:
```
Error: expression stack.empty is void and has no value
```
I can solve this by importing std.array: empty in the method
instead of the struct, but for my understanding of import
statements in structs I'd appreciate if someone explained what
these errors mean and why exactly they occur.
Thanks.
