## What's pseudorandom number generation? 1. Numbers appear to be randomly generated but in reality they are not *CORRECT* 2. Generating random numbers according to the physical laws 3. Generating pseudo even and odd numbers > **1:** Computers are deterministic machines. They can't generate truly random numbers (unlike actual physical processes). ## What's a seed number? 1. Exchanging of random numbers between two computers 2. It's used to getting a random number between 0 and the seed number 3. It's used initialize a pseduorandom number generator *CORRECT* ## Which package is used to generate pseudorandom numbers in Go? 1. pseudorand 2. rand *CORRECT* 3. random 4. randomizer ## What does [0, 5) mean? 1. A range of numbers between 0 and 5 (excluding 5) *CORRECT* 2. A range of numbers between 0 and 5 (including 5) 3. Just 0 and 5 4. Just 0 and 4 > **1:** Right. The square-brace means: "inclusion". The parenthesis means: "exclusion". So, [0, 5] means: 0, 1, 2, 3, 4. It's called the "mathematical interval notation". ## Why this function call would not work? ```go rand.Intn(0) ``` 1. First you should seed it 2. It expects two arguments 3. Intn works within a range of [0, 0). So, it doesn't make sense to include 0 and not include 0 at the same time. *CORRECT* > **1:** That's not the cause of this error. You don't always have to seed it. > **2:** No, it does not. ## What does this program print? Note that, each seed number below returns pseudorandom numbers as these: ``` Seed: 0 3 3 6 8 4 1 9 3 6 6 Seed: 1 1 1 9 3 2 4 7 6 6 6 Seed: 2 10 1 2 2 0 6 4 1 0 5 ``` Here's the program: ```go package main import ( "fmt" "math/rand" ) func main() { for i := 0; i < 3; i++ { rand.Seed(int64(i)) fmt.Print(rand.Intn(11), " ") fmt.Print(rand.Intn(11), " ") } } ``` 1. 3 1 10 3 1 1 2. 3 6 1 6 10 5 3. 1 10 1 1 3 3 4. 3 3 1 1 10 1 *CORRECT* > **4:** The numbers are determined depending on the seed number. So, this loop, seeds the pseudorandom generator with 0, 1, and 2 respectively. > > And, after each seed, it calls Intn twice to generate two random numbers. > > So, if you look at the result, 3 3 is the first two numbers of Seed: 0. 1 1 for Seed: 1. And, 10 1 for Seed: 2. ## What you should do if you want the pseudorandom generator to produce random numbers each time you run your program? 1. You need to seed it like this: rand.Seed(rand.Random) 2. You need to seed it like this: rand.Seed(time.Now().UnixNano()) *CORRECT* 3. You need to seed it like this: rand.Seed(time.Now())