Map, Filter and Reduce above collection of T in Golang

operations.go

package operations

type T struct {
  Code int
}

type TSequence []*T

type TMapFunc func(t *T) *T
type TFilterFunc func(t *T) bool
type TReduceFunc func(first *T, second *T) *T

func (seq TSequence) Map(mapper TMapFunc) TSequence {
  res := []*T{}
  for _, val := range seq {
    res = append(res, mapper(val))
  }

  return res
}

func (seq TSequence) Filter(filter TFilterFunc) TSequence {
  res := []*T{}
  for _, val := range seq {
    if filter(val) {
      res = append(res, val)
    }
  }

  return res
}

func (seq TSequence) Reduce(reducer TReduceFunc, init *T) *T {
  // initialize current value (first)
  curr := init
  // go over all values
  for _, val := range seq {
    curr = reducer(curr, val)
  }

  return curr
}