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