Math and Random

🎲 Go’s Magic Toolbox: Math & Random Numbers

Imagine you have a magic calculator that can do any math you want, and a mystery box that gives you surprise numbers. That’s what Go’s math and math/rand packages are!

🧮 Meet Your Math Helper

Think of the math package like having a super-smart friend who knows all the math tricks. You just ask, and they give you the answer instantly!

Getting Started

import "math"

That’s it! Now you have superpowers! 🦸

➕ Basic Math Operations

Absolute Value - “How Far From Zero?”

Imagine you’re standing at your house (that’s zero). Whether you walk 5 steps forward (+5) or 5 steps backward (-5), you still walked 5 steps total.

distance1 := math.Abs(-7.5)  // 7.5
distance2 := math.Abs(7.5)   // 7.5

🎯 Real life: Calculating how far you traveled, no matter which direction!

Floor & Ceil - “Rounding to Whole Numbers”

Floor is like dropping a ball - it falls DOWN to the nearest whole number.

Ceil (ceiling) is like a balloon - it floats UP to the nearest whole number.

dropped := math.Floor(3.7)   // 3
floated := math.Ceil(3.2)    // 4

// Even with negatives!
math.Floor(-2.3)  // -3 (goes down)
math.Ceil(-2.3)   // -2 (goes up)

graph TD
    A["3.7"] --> B{Which way?}
    B -->|Floor ⬇️| C["3"]
    B -->|Ceil ⬆️| D["4"]

Round - “The Fairest Choice”

Round looks at the decimal. If it’s 0.5 or more, go up. Otherwise, go down.

math.Round(2.4)   // 2
math.Round(2.5)   // 3
math.Round(2.6)   // 3

Min & Max - “Who’s the Winner?”

Like a race! Max finds the fastest, Min finds the slowest.

bigger := math.Max(10.5, 20.3)   // 20.3
smaller := math.Min(10.5, 20.3) // 10.5

Power - “Multiplying By Itself”

Pow is like asking: “What if I multiply this number by itself… many times?”

// 2 × 2 × 2 = 8
result := math.Pow(2, 3)  // 8

// 5 × 5 = 25
square := math.Pow(5, 2)  // 25

Square Root - “The Reverse of Squaring”

If 5 × 5 = 25, then the square root of 25 is 5. It’s like asking: “What number, times itself, gives me this?”

math.Sqrt(25)   // 5
math.Sqrt(100)  // 10
math.Sqrt(2)    // 1.414...

Special Math Constants

Go gives you some magic numbers that mathematicians love:

math.Pi      // 3.14159... (circles!)
math.E       // 2.71828... (growth!)
math.Phi     // 1.61803... (golden ratio!)

🎲 The Mystery Box: Random Numbers

Now for the fun part! The math/rand package is like having a mystery box that gives you surprise numbers.

Getting Started with Random

import (
    "math/rand"
    "time"
)

🌱 The Seed: Where Random Begins

Here’s a secret: computers can’t really be “random.” They follow patterns. The seed is the starting point of that pattern.

Same seed = Same “random” numbers every time!

// Old way (before Go 1.20)
rand.Seed(time.Now().UnixNano())

// New way (Go 1.20+) - automatic!
// Just use rand functions directly

Think of it like a music playlist on “shuffle.” If you start at the same point, you get the same order!

🎯 Getting Random Numbers

Random Integer (0 to n-1)

// Random number from 0 to 99
num := rand.Intn(100)

// Random dice roll (1 to 6)
dice := rand.Intn(6) + 1

Random Float (0.0 to 1.0)

// Random decimal between 0 and 1
fraction := rand.Float64()  // 0.234567...

Random in a Range

Want a number between 50 and 100?

min := 50
max := 100
num := rand.Intn(max-min+1) + min

graph TD
    A["Want 50-100"] --> B["Calculate range: 51"]
    B --> C["rand.Intn 51 gives 0-50"]
    C --> D["Add 50"]
    D --> E["Result: 50-100!"]

🔀 Shuffling Things

Want to mix up a list? Like shuffling cards!

cards := []string{"A", "2", "3", "4", "5"}
rand.Shuffle(len(cards), func(i, j int) {
    cards[i], cards[j] = cards[j], cards[i]
})
// Now cards are in random order!

🎰 Picking Random Items

colors := []string{"red", "blue", "green"}
picked := colors[rand.Intn(len(colors))]
// picked is a random color!

🆕 Go 1.20+ Modern Random

Go got even better! Now you can create your own random source:

// Create a new random source
r := rand.New(rand.NewSource(time.Now().UnixNano()))

// Use it
num := r.Intn(100)

This is helpful when you want different random streams that don’t interfere with each other!

🎮 Putting It All Together

Here’s a mini game: Guess the number!

package main

import (
    "fmt"
    "math"
    "math/rand"
)

func main() {
    secret := rand.Intn(10) + 1  // 1-10
    guess := 7

    diff := math.Abs(float64(secret - guess))

    if diff == 0 {
        fmt.Println("Perfect guess!")
    } else if diff <= 2 {
        fmt.Println("So close!")
    } else {
        fmt.Println("Keep trying!")
    }
}

🌟 Quick Summary

💡 Remember!

1. 📦 Import math for calculations, math/rand for randomness
2. 🌱 Seed your random (or use Go 1.20+ for auto-seeding)
3. 🎯 Intn(n) gives you 0 to n-1, so add 1 if you need 1 to n
4. 🧮 Abs makes negatives positive
5. ⬇️⬆️ Floor goes down, Ceil goes up

Now you have the keys to Go’s math kingdom! Go calculate something awesome! 🚀