Advanced Generics – Type Sets & Constraints

Type Sets (Go 1.18+)

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

A type set enumerates allowed types for a type parameter.

type Number interface { ~int | ~int64 | ~float64 }

func Sum[T Number](vals []T) T { var s T; for _, v := range vals { s += v }; return s }

Interface constraints with methods

type Stringer interface { String() string }

func Join[T Stringer](elems []T, sep string) string {
    var sb strings.Builder
    for i, e := range elems {
        if i > 0 { sb.WriteString(sep) }
        sb.WriteString(e.String())
    }
    return sb.String()
}

Using generic structs with methods

type Stack[T any] struct { items []T }
func (s *Stack[T]) Push(v T) { s.items = append(s.items, v) }
func (s *Stack[T]) Pop() (T, bool) {
    if len(s.items) == 0 { var zero T; return zero, false }
    idx := len(s.items) - 1
    v := s.items[idx]
    s.items = s.items[:idx]
    return v, true
}