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to Accumulate in the Go Track

Published at Feb 06 2019 · 0 comments
Test suite

Implement the accumulate operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.

Given the collection of strings:

  • "cat", "Dog", "b4t", "gO"

And the operation:

  • upcase a string

Your code should be able to produce the collection of strings:

  • "CAT", "DOG", "B4T, "GO"

Check out the test suite to see the expected function signature.


Keep your hands off that collect/map/fmap/whatchamacallit functionality provided by your standard library! Solve this one yourself using other basic tools instead.

Running the tests

To run the tests run the command go test from within the exercise directory.

If the test suite contains benchmarks, you can run these with the --bench and --benchmem flags:

go test -v --bench . --benchmem

Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.

Further information

For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.


Conversation with James Edward Gray II https://twitter.com/jeg2

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


package accumulate

import (

func echo(c string) string {
	return c

func capitalize(word string) string {
	return strings.Title(word)

var tests = []struct {
	expected    []string
	given       []string
	converter   func(string) string
	description string
	{[]string{}, []string{}, echo, "echo"},
	{[]string{"echo", "echo", "echo", "echo"}, []string{"echo", "echo", "echo", "echo"}, echo, "echo"},
	{[]string{"First", "Letter", "Only"}, []string{"first", "letter", "only"}, capitalize, "capitalize"},
	{[]string{"HELLO", "WORLD"}, []string{"hello", "world"}, strings.ToUpper, "strings.ToUpper"},

func TestAccumulate(t *testing.T) {
	for _, test := range tests {
		actual := Accumulate(test.given, test.converter)
		if fmt.Sprintf("%q", actual) != fmt.Sprintf("%q", test.expected) {
			t.Fatalf("Accumulate(%q, %q): expected %q, actual %q", test.given, test.description, test.expected, actual)

func BenchmarkAccumulate(b *testing.B) {
	for i := 0; i < b.N; i++ {

		for _, test := range tests {
			Accumulate(test.given, test.converter)

package accumulate

// Accumulate converts the given list according to the given function
func Accumulate(given []string, converter func(string) string) []string {
	result := given
	for i, s := range given {
		result[i] = converter(s)
	return result

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