Go Generics

Generics let one function work with many types. Type parameters go in square brackets.

ExampleGo

package main

import "fmt"

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

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

func Map[T, U any](items []T, f func(T) U) []U {
  out := make([]U, 0, len(items))
  for _, v := range items {
    out = append(out, f(v))
  }
  return out
}

func main() {
  fmt.Println(Sum([]int{1, 2, 3}))
  fmt.Println(Sum([]float64{1.5, 2.5}))
  fmt.Println(Map([]int{1, 2, 3}, func(n int) string { return fmt.Sprint(n * 10) }))
}

Output

6
4
[10 20 30]

Quick check

What is T in func Sum[T Number]?

A type parameterA variableA package

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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