On Sunday, 31 October 2021 at 16:54:35 UTC, pascal111 wrote:
Hi! I'm C learner and found the high similarity between C and
D, and was converting C code into D but couldn't get the
equivalent of this C statement "srand(time(NULL));".
Since D gives you access to the C standard library, you can use
pretty much exactly the same code in D:
```d
import core.stdc.stdlib; // bindings for <stdlib.h>
import core.stdc.time; // bindings for <time.h>
srand(time(null)); // null is lower-case in D
```
If you want to use D's standard library, you can instead use
[`std.random.rndGen`][1], the default random number generator.
Its documentation says:
It is allocated per-thread and initialized to an unpredictable
value for each thread.
In other words, it is seeded for you automatically. So when you
are converting C code that uses `rand` to D code that uses
`rndGen`, you can simply delete the line `srand(time(NULL));`,
and it will work ask expected.
If you wanted to seed it yourself, however, you would do it using
the `.seed` method, and generate the seed using
[`std.random.unpredictableSeed`][2].
```d
import std.random;
rndGen.seed(unpredictableSeed());
```
This is mainly useful when you are using a custom RNG instead of
the default `rndGen`, since custom RNGs are *not* automatically
seeded.
[1]: https://phobos.dpldocs.info/std.random.rndGen.html
[2]:
https://phobos.dpldocs.info/std.random.unpredictableSeed.1.html
