Go 1.18 Playground

package main

import (
    "fmt"
    "strconv"
)

// This playground uses a development build of Go:
// devel go1.18-3d3f5d912b Wed Jan 12 01:49:33 2022 +0000

func Map[T, R any](s []T, fn func(T)R) []R {
  var ret []R
  for _, v := range s {
    ret = append(ret, fn(v))
  }
  return ret
}

func Filter[T any](s []T, fn func(T) bool) []T {
  var ret []T
  for _, v := range s {
    if fn(v) {
      ret = append(ret, v)
    }
  }
  return ret
}

func Collect[T, R any](s []T, acc R, fn func(T, R) R) R {
  ret := acc
  for _, v := range s {
    ret = fn(v, ret)
  }
  return ret
}

func tryParse[T,R any](input T, parser func(T) (R, error)) R {
  r, _ := parser(input)
  return r
}

func main() {
  k := []string{"a","b","c"}
  r := Map(k, func(s string) string {
    return "x"+s
  })
  fmt.Println(r)
  r = Filter(k, func(s string) bool {
    return s == "a"
  })
  fmt.Println(r)
  x := []int{1,2,3}
  sum := Collect(x, 0, func(a,b int) int {
    return a+b
  })
  fmt.Println(sum)
  p := tryParse("12",strconv.Atoi)
  fmt.Println(p)
}