Re: passing a variadic parameter to randomSample

[vit via Digitalmars-d-learn]

On Tuesday, 25 January 2022 at 09:48:25 UTC, forkit wrote:

so I'm trying to write (or rather learn how to write) a 'variadic template function', that returns just one of its variadic parameter, randomly chosen.

But can't get my head around the problem here :-(

.. Error: template `std.random.randomSample` cannot deduce function from argument types `

// --

module test;
import std;

string RandomChoice(R...)(R r)
{
    auto rnd = MinstdRand0(42);
    return r.randomSample(1, rnd).to!string;
}

void main()
{
    writeln( RandomChoice("typeA", "typeB", "typeC") );
}

// --

`r` is not input range, try this:

```d
module test;
import std;


string RandomChoice1(R...)(R r)
{
    auto rnd = MinstdRand0(unpredictableSeed);
    return only(r).randomSample(1, rnd).front;
}

string RandomChoice2(R...)(R r)@nogc
{
        auto rnd = MinstdRand0(unpredictableSeed);

    switch(rnd.front % R.length){
        static foreach(enum I, alias arg; r){
                case I:
                return arg;
        }

        default:
                assert(0, "no impl");
    }
}

void main()
{
    writeln( RandomChoice1("typeA", "typeB", "typeC") );
    writeln( RandomChoice2("typeA", "typeB", "typeC") );
}
```