avg.go

package vector

import (
  "math"
)

func (vector *Vector) Sum() float64 {
	return vector.memoize("sum", func() float64 {
		sum := 0.0
		for _, v := range vector.values {
			sum += v
		}
		return sum
	})
}

vector.go

package vector

type Vector struct {
  values   []float64
	memoized map[string]float64
}

type generator func() float64

func New(values []float64) *Vector {
	return &Vector{values: values, memoized: make(map[string]float64)}
}

func (vector *Vector) memoize(key string, f generator) float64 {
	_, found := vector.memoized[key]
	if !found {
		vector.memoized[key] = f()
	}
	return vector.memoized[key]
}