learngo/09-go-type-system/03-predeclared-types/main.go

// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials  : https://learngoprogramming.com
// In-person training  : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus

package main

import (
	"fmt"
	"math"
	"unsafe"
)

func main() {
	// you can find the limits of numerics types
	// in the math package
	fmt.Println("int8   :", math.MinInt8, math.MaxInt8)
	fmt.Println("int16  :", math.MinInt16, math.MaxInt16)
	fmt.Println("int32  :", math.MinInt32, math.MaxInt32)
	fmt.Println("int64  :", math.MinInt64, math.MaxInt64)

	// unsigned type can only represent positive integers
	fmt.Println("uint8  :", 0, math.MaxUint8)
	fmt.Println("uint16 :", 0, math.MaxUint16)
	fmt.Println("uint32 :", 0, math.MaxUint32)
	fmt.Println("uint64 :", 0, uint64(math.MaxUint64))
	// You can't print MaxUint64 directly
	// Its size is way bigger for the runtime
	// It can only be used in constant expressions

	// e means zeros after the number (scientific notation)
	// 1e1, is 10 1e2, is 100, 12e1 is 120
	fmt.Println("float32:", math.SmallestNonzeroFloat32,
		math.MaxFloat32)
	fmt.Println("float64:", math.SmallestNonzeroFloat64,
		math.MaxFloat64)

	// memory costs
	fmt.Println("int    :", unsafe.Sizeof(int(1)), "bytes")
	fmt.Println("int8   :", unsafe.Sizeof(int8(1)), "bytes")
	fmt.Println("int16  :", unsafe.Sizeof(int16(1)), "bytes")
	fmt.Println("int32  :", unsafe.Sizeof(int32(1)), "bytes")
	fmt.Println("int64  :", unsafe.Sizeof(int64(1)), "bytes")

	fmt.Println("uint   :", unsafe.Sizeof(uint(1)), "bytes")
	fmt.Println("uint8  :", unsafe.Sizeof(uint8(1)), "bytes")
	fmt.Println("uint16 :", unsafe.Sizeof(uint16(1)), "bytes")
	fmt.Println("uint32 :", unsafe.Sizeof(uint32(1)), "bytes")
	fmt.Println("uint64 :", unsafe.Sizeof(uint64(1)), "bytes")

	fmt.Println("float32:", unsafe.Sizeof(float32(1)), "bytes")
	fmt.Println("float64:", unsafe.Sizeof(float64(1)), "bytes")

	fmt.Println("hello  :", len("hello")+8, "bytes")
	fmt.Println("hi     :", len("hi")+8, "bytes")
	fmt.Println("hi     :", len("hi")+8, "bytes")
}