Re: Pass enum variable as const ref arg
On Friday, 4 December 2020 at 12:54:25 UTC, Andrey wrote: [...] WTF? If you come from a C or C++ background, it's quite reasonable to think of enum stuff like a #define macro. You're using static arrays, but note that array literals allocate in many use cases. It really is like a C/C++ macro. Use n times = allocate n times. You avoid that with a static immutable completely. That said, if you use the value of that enum only at compile-time, there's no need for a static immutable. Hope that this rule of thumb sheds some more light on how to achieve certain stuff.
Re: Pass enum variable as const ref arg
On Friday, 4 December 2020 at 12:54:25 UTC, Andrey wrote:
Hello,
void test(const ref string[3] qazzz) { qazzz.writeln; }
void main()
{
enum string[3] value = ["qwer", "ggg", "v"];
test(value);
}
Gives errors:
It works if you pass `-preview=rvaluerefparam` to the compiler.
But the other suggestions are better IMO.
—Bastiaan.
Re: Pass enum variable as const ref arg
Thank you!
Re: Pass enum variable as const ref arg
On Friday, 4 December 2020 at 13:42:45 UTC, Andrey wrote: Hm, you mean that enum variable is not a real variable? I thought that to make CT variable you should mark it as enum (in c++ as constexpr). How to do it here? The official name for what you're calling an "enum variable" is "manifest constant" [1]. Manifest constants are like named literals: when you use one, it is treated by the compiler as though you had copy-and-pasted its value at that point in the code. So, for example, enum string[3] value = ["qwer", "ggg", "v"]; test(value); ...is equivalent to test(cast(string[3]) ["qwer", "ggg", "v"]); If you want to declare a compile-time constant that's also an lvalue, you can use `static immutable` instead of `enum`: static immutable string[3] value = ["qwer", "ggg", "v"]; test(value); [1] https://dlang.org/spec/enum.html#manifest_constants
Re: Pass enum variable as const ref arg
On 05/12/2020 2:42 AM, Andrey wrote: Hm, you mean that enum variable is not a real variable? It is not a variable. It is a constant that cannot be changed and does not exist in the executable. I thought that to make CT variable you should mark it as enum (in c++ as constexpr). How to do it here? You are already doing it. This is not what you want. You want a variable that will pass by ref. Remove enum.
Re: Pass enum variable as const ref arg
Hm, you mean that enum variable is not a real variable? I thought that to make CT variable you should mark it as enum (in c++ as constexpr). How to do it here?
Re: Pass enum variable as const ref arg
On 05/12/2020 1:54 AM, Andrey wrote:
Hello,
void test(const ref string[3] qazzz) { qazzz.writeln; }
void main()
{
enum string[3] value = ["qwer", "ggg", "v"];
That is a compile time constant (remove the enum).
test(value);
}
Gives errors:
onlineapp.d(26): Error: function onlineapp.test(ref const(string[3])
qazzz) is not callable using argument types (string[3])
onlineapp.d(26): cannot pass rvalue argument ["qwer", "ggg",
"v"] of type string[3] to parameter ref const(string[3]) qazzz
WTF?
The ref. The problem is the ref. You are passing it a constant, not a
variable.
Pass enum variable as const ref arg
Hello,
void test(const ref string[3] qazzz) { qazzz.writeln; }
void main()
{
enum string[3] value = ["qwer", "ggg", "v"];
test(value);
}
Gives errors:
onlineapp.d(26): Error: function onlineapp.test(ref
const(string[3]) qazzz) is not callable using argument types
(string[3])
onlineapp.d(26):cannot pass rvalue argument ["qwer",
"ggg", "v"] of type string[3] to parameter ref const(string[3])
qazzz
WTF?
