main.go

// Demonstrates built-in types: numbers, strings, arrays, slices, maps, structs.
package main

import (
	"fmt"
	"strings"
)

type Point struct {
	X, Y int
}

type Animal struct{ Name string }

func (a Animal) Speak() string { return a.Name + " makes a sound" }

type Dog struct {
	Animal
	Breed string
}

func main() {
	var i int = 65
	f := float64(i)
	r := rune(i)
	fmt.Printf("int=%d float=%v rune=%c\n", i, f, r)

	s := "héllo"
	fmt.Println("byte len:", len(s))
	for i, r := range s {
		fmt.Printf("  byte %d -> %c (U+%04X)\n", i, r, r)
	}

	var b strings.Builder
	for k := 0; k < 5; k++ {
		fmt.Fprintf(&b, "x%d ", k)
	}
	fmt.Println("built:", b.String())

	arr := [3]int{1, 2, 3}
	cp := arr
	cp[0] = 99
	fmt.Println("array value semantics:", arr, cp)

	sl := []int{1, 2, 3, 4, 5}
	sub := sl[1:4]
	sub[0] = 99
	fmt.Println("slices share backing:", sl, sub)

	m := map[string]int{"a": 1, "b": 2}
	m["c"] = 3
	if v, ok := m["x"]; ok {
		fmt.Println("found", v)
	} else {
		fmt.Println("'x' missing, zero is", v)
	}
	delete(m, "a")
	fmt.Println("map:", m)

	p := Point{X: 1, Y: 2}
	fmt.Println("struct:", p)

	d := Dog{Animal: Animal{Name: "Rex"}, Breed: "Lab"}
	fmt.Println("embedded:", d.Name, "|", d.Speak(), "|", d.Breed)

	q := &Point{3, 4}
	q.X = 30
	fmt.Println("pointer:", *q)
}