• Andrey (3/16) Dec 04 2020 WTF?
• rikki cattermole (4/22) Dec 04 2020 The ref. The problem is the ref. You are passing it a constant, not a
• Andrey (4/4) Dec 04 2020 Hm, you mean that enum variable is not a real variable?
• rikki cattermole (5/9) Dec 04 2020 It is not a variable. It is a constant that cannot be changed and does
• Paul Backus (15/19) Dec 04 2020 The official name for what you're calling an "enum variable" is
• Andrey (1/1) Dec 04 2020 Thank you!
• Bastiaan Veelo (4/13) Dec 04 2020 It works if you pass `-preview=rvaluerefparam` to the compiler.
• Q. Schroll (10/12) Dec 08 2020 If you come from a C or C++ background, it's quite reasonable to

Andrey <saasecondbox yandex.ru> writes:

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?

rikki cattermole <rikki cattermole.co.nz> writes:

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.

Andrey <saasecondbox yandex.ru> writes:

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?

rikki cattermole <rikki cattermole.co.nz> writes:

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.

Paul Backus <snarwin gmail.com> writes:

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

Andrey <saasecondbox yandex.ru> writes:

Thank you!

Bastiaan Veelo <Bastiaan Veelo.net> writes:

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.

Q. Schroll <qs.il.paperinik gmail.com> writes:

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.