/**
Basic types
Go's basic types are
bool
string
int int8 int16 int32 int64
uint uint8 uint16 uint32 uint64 uintptr
float32 float64
complex64 complex128
**/
var (
ToBe bool = false
MaxInt uint64 = 1<<64 - 1
z complex128 = cmath.Sqrt(-5 + 12i)
)
func main() {
const f = "%T(%v)\n"
fmt.Printf(f, ToBe, ToBe)
fmt.Printf(f, MaxInt, MaxInt)
fmt.Printf(f, z, z)
}
func main() {
fmt.Println("--------------- section 1 ----------------")
var s1 string = "this is a string"
fmt.Println(s1)
// type inferred
var s2 = "this is another string"
fmt.Println(s2)
// shorthand
s3 := "this is yet another string"
fmt.Println(s3)
// working with strings
fmt.Println(s3[5] == 'i')
// assigns a new string to variable, doesn't change contents string
s3 = "that could be a string"
fmt.Println(s3[5] == 'i')
// s3[5] = 'a' // error: invalid left hand side of argument
fmt.Println("--------------- section 2 ----------------")
// working with other native types
var a int = 4 // machine-size (32bit or 64bit)
var b int8 = -128 // byte (signed)
var bu uint8 = 255 // byte (unsigned)
var w int16 = -32768 // word (16bits) (signed)
var wu uint16 = 65535 // word (16bits) (unsigned)
var dw int32 = -1000000 // dword (32bits) (signed)
var du uint32 = 1000000 // dword (32bits) (unsigned)
var qw int64 = -100000000000000 // qword (64bits) (signed)
var qu uint64 = 100000000000000 // qword (64bits) (unsigned)
var f3 float32 = 3.1415999999999 // 32bit float
var f6 float64 = 3.1415999999999 // 64bit float
var c3 complex64 = complex(1.0, 1.0) // 2x32bit complex float
var c6 complex128 = complex(0.0, 1.0) // 2x64bit complex float
fmt.Println(a, b, bu, w, wu, dw, du, qw, qu)
fmt.Println(a + 10)
fmt.Println(qu + 10)
fmt.Println(f3, f6, c3, c6)
fmt.Println(c3 * c3)
fmt.Println(cmath.Sqrt(-1))
// fmt.Println(a + b) // error: incompatible types in binary expression
// arrays
var arrA [5]int = [5]int{1, 2, 3, 5, 8} // or = [...]int{1,2,3,5,8], compiler counts
fmt.Println(arrA)
fmt.Println(arrA[3])
var arrB [6]int
// arrB = arrA // error: incompatible types in assignment
var sliceB []int
sliceB = arrA[:] // converts array to slice
fmt.Println(sliceB)
sliceB = arrA[1:3] // converts array to slice
fmt.Println(sliceB)
arrA[1] = 9999 // array are values, but slices are references
fmt.Println(sliceB)
for i := 0; i < len(arrA); i++ {
fmt.Println("loop test ", i, arrA[i])
}
for i, v := range arrA {
fmt.Println("loop test ", i, v)
}
// maps
var mapA map[string]int
// mapA["test"] = 54 // panic: runtime error: invalid memory address or nil pointer dereference
mapA = make(map[string]int) // maps are references, and must be allocated first
mapA["test"] = 54
mapA["hello"] = 985
fmt.Println(mapA)
fmt.Println("--------------- section 3 ----------------")
// returning from main yields exit code 0
os.Exit(123)
}
