Random Numbers

Here, we create a new prng using a 64-bit random seed. a, b, c, and d are given random values via this prng. The expressions giving c and d values are equivalent. DefaultPrng is Xoroshiro128; there are other prngs available in std.rand.

const std = @import("std");

test "random numbers" {
    var prng = std.rand.DefaultPrng.init(blk: {
        var seed: u64 = undefined;
        try std.posix.getrandom(std.mem.asBytes(&seed));
        break :blk seed;
    });
    const rand = prng.random();

    const a = rand.float(f32);
    const b = rand.boolean();
    const c = rand.int(u8);
    const d = rand.intRangeAtMost(u8, 0, 255);

    //suppress unused constant compile error
    _ = .{ a, b, c, d };
}

Cryptographically secure random is also available.

const std = @import("std");

test "crypto random numbers" {
    const rand = std.crypto.random;

    const a = rand.float(f32);
    const b = rand.boolean();
    const c = rand.int(u8);
    const d = rand.intRangeAtMost(u8, 0, 255);

    //suppress unused constant compile error
    _ = .{ a, b, c, d };
}

info

We can now use our knowledge of std.rand and make a guessing game together.