Go 1.18 - Generics

0- Go 1.18 - Generics.md

Go 1.18 - Generics

Go 1.18 will be a significant release and contains a lot of new features. One of them is generics which you can experiment yourself with using either the playground or gotip.

Examples:

1. Any constraint
2. Ordered constraint (one of many built-in ones)
3. Custom constraint
4. Custom generic type

---

Reference: https://bitfieldconsulting.com/golang/generics

1-any-constraint.go

// Go 1.17
func ValToPtr(val interface{}) *interface{} {
    return &val
}

strPtr := ValToPtr("Foo")
integerPtr := ValToPtr(1)

// Go 1.18
func ValToPtr[T any](val T) *T {
    return &val
}

strPtr := ValToPtr("Foo")
integerPtr := ValToPtr(1)

2-ordered-constraint.go

// Go 1.17
func MaxInt(input []int) (max int) {
    for _, v := range input {
        if v > max {
            max = v
        }
    }
    return max
}

func MaxFloat32(input []float32) (max float32) {
    for _, v := range input {
        if v > max {
            max = v
        }
    }
    return max
}

maxFloat32 := MaxFloat32([]float32{1.2, 8.2, 4.2})
maxInt := MaxInt([]int{1, 8, 4})

// Go 1.18
func Max[T constraints.Ordered](input []T) (max T) {
    for _, v := range input {
        if v > max {
            max = v
        }
    }
    return max
}

maxFloat32 := Max([]float32{1.2, 8.2, 4.2})
maxInt := Max([]int{1, 8, 4})

3-custom-constraint.go

// Go 1.17
func DoStuffForStr(val string) {
    // Do stuff
}

func DoStuffForInt(val int) {
    // Do stuff
}

DoStuffForStr("1")
DoStuffForInt(1)

// Go 1.18
type CustomConstraint interface {
    type string, int
}

func DoStuff[T CustomConstraint](val T) {
    // Do stuff
}

DoStuff("1")
DoStuff(1)

4-custom-generic-type.go

// Go 1.17
type StrCollection []string

func (c StrCollection) Print() {
    // Do stuff
}

type IntCollection []int

func (c IntCollection) Print() {
    // Do stuff
}

coll1 := StrCollection{"1", "2", "3"}
coll1.Print()

coll2 := IntCollection{1, 2, 3}
coll2.Print()

// Go 1.18
type CustomConstraint interface {
    type string, int
}
type Collection[T CustomConstraint] []T

func (c Collection[T]) Print() {
    // Do stuff
}

coll1 := Collection[T string]{"1", "2", "3"}
coll1.Print()

coll2 := Collection[T int]{1, 2, 3}
coll2.Print()