On Saturday, 2 December 2023 at 13:16:26 UTC, Johannes
Miesenhardt wrote:
Hello,
I am trying to learn D and I have stumbled upon an issue
Consider this code:
```d
import std.stdio;
//version = Test;
int main() {
version (Test) {
writeln("Hello, world!");
}
return 0;
}
```
This compiles, however what if we want to turn the version
statement around?
I first expected `version (!Test)` to work, but it doesn't
since the grammar says:
```
VersionCondition:
version ( Identifier )
version ( unittest )
version ( assert )
```
We are using the first way, the one with the Identifier.
The reason inverting works with if-statements is because they
take an "Expression".
I see the way why it doesn't work, but I think it should.
Considering that
`version (Test) {} else {`
works without any issue but looks very ugly.
Can somebody explain if this is an intended decision or what I
should do instead of using my ugly replacement?
It depends what do you want to achieve, if you just want a bool
at the top of your module to toggle features, then you can do
this:
```D
import std.stdio;
enum Test = true;
int main() {
static if (Test == false) {
writeln("this will never be called, it won't be
compiled");
} else {
writeln("hello!");
}
return 0;
}
```
``static if`` is evaluated at compile time, you can mix it with
``version`` if you need to provide the flag during compilation
```D
import std.stdio;
version (Test)
enum HasTest = true;
else
enum HasTest = false;
int main() {
static if (HasTest == false) {
writeln("this will never be called, it won't be
compiled");
} else {
writeln("hello!");
}
return 0;
}
```
I wish we could use ``version`` as expression, to void the
repetition:
```D
import std.stdio;
enum HasTest = version (Test) ? true : false;
int main() {
static if (HasTest == false) {
writeln("this will never be called, it won't be
compiled");
} else {
writeln("hello!");
}
return 0;
}
```
If someone able to do it, would be cool to see a PR
