Merge Go Work

go/atbash-cipher/README.md

@@ -0,0 +1,46 @@
+# Atbash Cipher
+
+Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
+
+The Atbash cipher is a simple substitution cipher that relies on
+transposing all the letters in the alphabet such that the resulting
+alphabet is backwards. The first letter is replaced with the last
+letter, the second with the second-last, and so on.
+
+An Atbash cipher for the Latin alphabet would be as follows:
+
+```plain
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: zyxwvutsrqponmlkjihgfedcba
+```
+
+It is a very weak cipher because it only has one possible key, and it is
+a simple monoalphabetic substitution cipher. However, this may not have
+been an issue in the cipher's time.
+
+Ciphertext is written out in groups of fixed length, the traditional group size
+being 5 letters, and punctuation is excluded. This is to make it harder to guess
+things based on word boundaries.
+
+## Examples
+- Encoding `test` gives `gvhg`
+- Decoding `gvhg` gives `test`
+- Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `The quick brown fox jumps over the lazy dog.`
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+Wikipedia [http://en.wikipedia.org/wiki/Atbash](http://en.wikipedia.org/wiki/Atbash)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/atbash-cipher/atbash.go

@@ -0,0 +1,36 @@
+package atbash
+
+import "strings"
+
+func Atbash(s string) string {
+	s = strings.ToLower(s)
+	var v []byte
+	var b, iter int
+	for i := range s {
+		sv := int(s[i])
+		switch {
+		case sv < 48:
+			continue
+		case sv >= 48 && sv <= 57:
+			b = sv
+		case sv < 109:
+			b = 110 + (109 - sv)
+		case sv == 109:
+			b = 110
+		case sv == 110:
+			b = 109
+		case sv > 110:
+			b = 109 - (sv - 110)
+		}
+		v = append(v, byte(b))
+		iter++
+		if iter == 5 {
+			v = append(v, ' ')
+			iter = 0
+		}
+	}
+	if iter == 0 {
+		return string(v)[:len(string(v))-1]
+	}
+	return string(v)
+}

go/atbash-cipher/atbash_cipher_test.go

@@ -0,0 +1,40 @@
+package atbash
+
+import "testing"
+
+var tests = []struct {
+	expected string
+	s        string
+}{
+	{"ml", "no"},
+	{"ml", "no"},
+	{"bvh", "yes"},
+	{"lnt", "OMG"},
+	{"lnt", "O M G"},
+	{"nrmwy oldrm tob", "mindblowingly"},
+	{"gvhgr mt123 gvhgr mt", "Testing, 1 2 3, testing."},
+	{"gifgs rhurx grlm", "Truth is fiction."},
+	{"gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt", "The quick brown fox jumps over the lazy dog."},
+}
+
+func TestAtbash(t *testing.T) {
+	for _, test := range tests {
+		actual := Atbash(test.s)
+		if actual != test.expected {
+			t.Errorf("Atbash(%s): expected %s, actual %s", test.s, test.expected, actual)
+		}
+	}
+}
+
+func BenchmarkAtbash(b *testing.B) {
+	b.StopTimer()
+	for _, test := range tests {
+		b.StartTimer()
+
+		for i := 0; i < b.N; i++ {
+			Atbash(test.s)
+		}
+
+		b.StopTimer()
+	}
+}

go/atbash-cipher/cmd/main.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"fmt"
+
+	"../../atbash-cipher"
+)
+
+func main() {
+	fmt.Println(atbash.Atbash("mindblowingly"))
+}

go/current

@@ -1 +1 @@
-custom-set
+prime-factors

go/custom-set/cmd/main.go

@@ -11,9 +11,9 @@ func main() {
 	s1 := stringset.NewFromSlice([]string{"a"})
 	addAndOutput(s1, "b")
 	addAndOutput(s1, "d")
+	addAndOutput(s1, "c")
 	s1.PrettyPrint()
 	return
-	addAndOutput(s1, "c")
 	addAndOutput(s1, "0")
 	addAndOutput(s1, "aa")
 	addAndOutput(s1, "aaa")

go/custom-set/custom_set_test.go

@@ -27,7 +27,6 @@ package stringset
 // Format the empty set as {}.
 
 import (
-	"fmt"
 	"math/rand"
 	"reflect"
 	"strconv"
@@ -167,17 +166,13 @@ func TestEqual(t *testing.T) {
 // helper for testing Add, Delete
 func testEleOp(name string, op func(Set, string), cases []eleOpCase, t *testing.T) {
 	for _, tc := range cases {
-		fmt.Print("Running Test Case: ")
-		fmt.Println(tc)
 		s := NewFromSlice(tc.set)
 		op(s, tc.ele)
 		want := NewFromSlice(tc.want)
 		if !Equal(s, want) {
-			fmt.Println(s.String())
 			t.Fatalf("%v %s %q = %v, want %v",
 				NewFromSlice(tc.set), name, tc.ele, s, want)
 		}
-		fmt.Println("=== Done ===")
 	}
 }
 

go/custom-set/stringset.go

@@ -3,7 +3,6 @@ package stringset
 import (
 	"errors"
 	"fmt"
-	"strconv"
 	"strings"
 )
 
@@ -45,20 +44,12 @@ func (s Set) Add(v string) {
 		return
 	}
 	if !s.Has(v) {
-		bef := "Current Top Node: " + s.top.value + ";L:" + s.top.getLeftValue() + ";R:" + s.top.getRightValue()
 		newNode := s.top.Add(&Node{value: v})
-		fmt.Println(bef)
-		fmt.Println("Current New Node: " + newNode.value + ";L:" + newNode.getLeftValue() + ";R:" + newNode.getRightValue())
-		fmt.Printf("newNode.left: %v (%v)\n", &newNode.left, newNode.left)
+
 		s.top.value = newNode.value
 		s.top.left = newNode.left
 		s.top.right = newNode.right
-		fmt.Println("Current Top Node: " + s.top.value + ";L:" + s.top.getLeftValue() + ";R:" + s.top.getRightValue())
-		fmt.Printf("s.top.left: %v (%v)\n", &s.top.left, s.top.left)
-		fmt.Println("Add Done")
 
-		//s.top = s.top.Add(newNode)
-		//fmt.Println("Current Top Node: " + s.top.value + ";L:" + s.top.getLeftValue() + ";R:" + s.top.getRightValue())
 	}
 }
 
@@ -274,63 +265,43 @@ func (sv *Node) findHome(v *Node) {
 }
 
 func (sv *Node) Add(n *Node) *Node {
-	fmt.Println("1 Adding at Node " + sv.value)
 	cmp := strings.Compare(n.value, sv.value)
 	if cmp < 0 {
-		fmt.Println("2 checking to left")
 		if sv.left == nil {
-			fmt.Println("3 left is nil, add it")
 			sv.left = n
 		} else {
-			fmt.Println("--> 4 recurse left")
 			sv.left = sv.left.Add(n)
-			fmt.Println("<-- 5 added to left")
 		}
 	} else {
-		fmt.Println("6 checking to right")
 		if sv.right == nil {
-			fmt.Println("7 right is nil, add it")
 			sv.right = n
 		} else {
-			fmt.Println("--> 8 recurse right")
 			sv.right = sv.right.Add(n)
-			fmt.Println("<-- 9 added to right")
 		}
 	}
 
-	fmt.Println("10 let's balance now (sv: " + sv.value + ")")
+	newVal := sv
+	/* TODO: Fix the tree balancing
 	balance := GetBalance(sv)
 	// left left unbalance
-	fmt.Println("11 balance: " + strconv.Itoa(balance))
-	newVal := sv
-	if balance > 1 && strings.Compare(n.value, sv.getLeftValue()) < 0 { // < sv.left.value {
-		fmt.Println("12 Left Left")
+	if balance > 1 && strings.Compare(n.value, sv.getLeftValue()) < 0 {
 		newVal = RightRotate(sv)
-		fmt.Println("13")
 	}
 	// right right unbalance
-	if balance < -1 && strings.Compare(n.value, sv.getRightValue()) > 0 { //n.value > sv.right.value {
-		fmt.Println("14 Right Right")
+	if balance < -1 && strings.Compare(n.value, sv.getRightValue()) > 0 {
 		newVal = LeftRotate(sv)
-		fmt.Println("15")
 	}
 	// left right unbalance
-	if balance > 1 && strings.Compare(n.value, sv.getLeftValue()) > 0 { //n.value > sv.left.value {
-		fmt.Println("16 Left Right")
+	if balance > 1 && strings.Compare(n.value, sv.getLeftValue()) > 0 {
 		sv.left = LeftRotate(sv.left)
-		fmt.Println("17")
 		newVal = RightRotate(sv)
-		fmt.Println("18")
 	}
 	// right left unbalance
-	if balance < -1 && strings.Compare(n.value, sv.getRightValue()) < 0 { //n.value < sv.right.value {
-		fmt.Println("19 Right Left")
+	if balance < -1 && strings.Compare(n.value, sv.getRightValue()) < 0 {
 		sv.right = RightRotate(sv.right)
-		fmt.Println("20")
 		newVal = LeftRotate(sv)
-		fmt.Println("21")
 	}
-	fmt.Println("22 end add")
+	*/
 	return newVal
 }
 
@@ -476,9 +447,6 @@ func RightRotate(y *Node) *Node {
 	// Perform rotation
 	x.right = y
 	y.left = t2
-	fmt.Println("RightRotate: return=" + x.value + "; L:" + x.left.value + "; R:" + x.right.value)
-	fmt.Println("RightRotate: leftNode=" + x.getLeftValue() + "; L:" + x.left.getLeftValue() + "; R:" + x.left.getRightValue())
-	fmt.Println("RightRotate: rightNode=" + x.getRightValue() + "; L:" + x.right.getLeftValue() + "; R:" + x.right.getRightValue())
 	// Return new root
 	return x
 }
@@ -490,9 +458,6 @@ func LeftRotate(x *Node) *Node {
 	y.left = x
 	x.right = t2
 	// Return new root
-	fmt.Println("LeftRotate: return=" + y.value + "; L:" + y.left.value + "; R:" + y.right.value)
-	fmt.Println("LeftRotate: leftNode=" + y.getLeftValue() + "; L:" + y.left.getLeftValue() + "; R:" + y.left.getRightValue())
-	fmt.Println("LeftRotate: rightNode=" + y.getRightValue() + "; L:" + y.right.getLeftValue() + "; R:" + y.right.getRightValue())
 	return y
 }
 

go/hello-world/README.md

@@ -0,0 +1,58 @@
+# Hello World
+
+Write a function that greets the user by name, or by saying "Hello, World!" if no name is given.
+
+["Hello, World!"](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program) is the traditional first program for beginning programming in a new language.
+
+**Note:** You can skip this exercise by running:
+
+    exercism skip $LANGUAGE hello-world
+
+## Specification
+
+Write a `Hello World!` function that can greet someone given their name.
+The function should return the appropriate greeting.
+
+For an input of "Alice", the response should be "Hello, Alice!".
+
+If a name is not given, the response should be "Hello, World!"
+
+## Test-Driven Development
+
+As programmers mature, they eventually want to test their code.
+
+Here at Exercism we simulate [Test-Driven Development](http://en.wikipedia.org/wiki/Test-driven_development) (TDD), where you write your tests before writing any functionality. The simulation comes in the form of a pre-written test suite, which will signal that you have solved the problem.
+
+It will also provide you with a safety net to explore other solutions without breaking the functionality.
+
+### A typical TDD workflow on Exercism:
+
+1. Run the test file and pick one test that's failing.
+2. Write some code to fix the test you picked.
+3. Re-run the tests to confirm the test is now passing.
+4. Repeat from step 1.
+5. Submit your solution (`exercism submit /path/to/file`)
+
+## Instructions
+
+Submissions are encouraged to be general, within reason. Having said that, it's also important not to over-engineer a solution.
+
+It's important to remember that the goal is to make code as expressive and readable as we can. However, solutions to the hello-world exercise will not be reviewed by a person, but by rikki- the robot, who will offer an encouraging word.
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+This is an exercise to introduce users to using Exercism [http://en.wikipedia.org/wiki/%22Hello,_world!%22_program](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/hello-world/hello_test.go

@@ -0,0 +1,29 @@
+package hello
+
+import "testing"
+
+// Define a function HelloWorld(string) string.
+//
+// Also define a testVersion with a value that matches
+// the targetTestVersion here.
+
+const targetTestVersion = 2
+
+func TestHelloWorld(t *testing.T) {
+	tests := []struct {
+		name, expected string
+	}{
+		{"", "Hello, World!"},
+		{"Gopher", "Hello, Gopher!"},
+	}
+	for _, test := range tests {
+		observed := HelloWorld(test.name)
+		if observed != test.expected {
+			t.Fatalf("HelloWorld(%s) = %v, want %v", test.name, observed, test.expected)
+		}
+	}
+
+	if testVersion != targetTestVersion {
+		t.Fatalf("Found testVersion = %v, want %v", testVersion, targetTestVersion)
+	}
+}

go/hello-world/hello_world.go

@@ -0,0 +1,11 @@
+package hello
+
+const testVersion = 2
+
+// HelloWorld takes a string (optionally empty) and says hello to it!
+func HelloWorld(s string) string {
+	if s == "" {
+		s = "World"
+	}
+	return "Hello, " + s + "!"
+}

go/phone-number/README.md

@@ -0,0 +1,38 @@
+# Phone Number
+
+Write a program that cleans up user-entered phone numbers so that they can be sent SMS messages.
+
+The rules are as follows:
+
+- If the phone number is less than 10 digits assume that it is bad
+  number
+- If the phone number is 10 digits assume that it is good
+- If the phone number is 11 digits and the first number is 1, trim the 1
+  and use the last 10 digits
+- If the phone number is 11 digits and the first number is not 1, then
+  it is a bad number
+- If the phone number is more than 11 digits assume that it is a bad
+  number
+
+We've provided tests, now make them pass.
+
+Hint: Only make one test pass at a time. Disable the others, then flip
+each on in turn after you get the current failing one to pass.
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+Event Manager by JumpstartLab [http://tutorials.jumpstartlab.com/projects/eventmanager.html](http://tutorials.jumpstartlab.com/projects/eventmanager.html)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/phone-number/phone_number_test.go

@@ -0,0 +1,118 @@
+package phonenumber
+
+import (
+	"testing"
+)
+
+type testCase struct {
+	input     string
+	expected  string
+	expectErr bool
+}
+
+var numberTests = []testCase{
+	{"(123) 456-7890", "1234567890", false},
+	{"123.456.7890", "1234567890", false},
+	{"1234567890", "1234567890", false},
+	{"12345678901234567", "", true},
+	{"21234567890", "", true},
+	{"123456789", "", true},
+}
+
+func TestNumber(t *testing.T) {
+	for _, test := range numberTests {
+		actual, actualErr := Number(test.input)
+		if actual != test.expected {
+			t.Errorf("Number(%s): expected [%s], actual: [%s]", test.input, test.expected, actual)
+		}
+		// if we expect an error and there isn't one
+		if test.expectErr && actualErr == nil {
+			t.Errorf("Number(%s): expected an error, but error is nil", test.input)
+		}
+		// if we don't expect an error and there is one
+		if !test.expectErr && actualErr != nil {
+			t.Errorf("Number(%s): expected no error, but error is: %s", test.input, actualErr)
+		}
+	}
+}
+
+func BenchmarkNumber(b *testing.B) {
+	b.StopTimer()
+	for _, test := range numberTests {
+		b.StartTimer()
+		for i := 0; i < b.N; i++ {
+			Number(test.input)
+		}
+		b.StopTimer()
+	}
+}
+
+var areaCodeTests = []testCase{
+	{"1234567890", "123", false},
+	{"213.456.7890", "213", false},
+	{"213.456.7890.2345", "", true},
+	{"213.456", "", true},
+}
+
+func TestAreaCode(t *testing.T) {
+	for _, test := range areaCodeTests {
+		actual, actualErr := AreaCode(test.input)
+		if actual != test.expected {
+			t.Errorf("AreaCode(%s): expected [%s], actual: [%s]", test.input, test.expected, actual)
+		}
+		// if we expect an error and there isn't one
+		if test.expectErr && actualErr == nil {
+			t.Errorf("AreaCode(%s): expected an error, but error is nil", test.input)
+		}
+		// if we don't expect an error and there is one
+		if !test.expectErr && actualErr != nil {
+			t.Errorf("AreaCode(%s): expected no error, but error is: %s", test.input, actualErr)
+		}
+	}
+}
+
+func BenchmarkAreaCode(b *testing.B) {
+	b.StopTimer()
+	for _, test := range areaCodeTests {
+		b.StartTimer()
+		for i := 0; i < b.N; i++ {
+			AreaCode(test.input)
+		}
+		b.StopTimer()
+	}
+}
+
+var formatTests = []testCase{
+	{"1234567890", "(123) 456-7890", false},
+	{"11234567890", "(123) 456-7890", false},
+	{"112345", "", true},
+	{"11234590870986", "", true},
+}
+
+func TestFormat(t *testing.T) {
+	for _, test := range formatTests {
+		actual, actualErr := Format(test.input)
+		if actual != test.expected {
+			t.Errorf("Format(%s): expected [%s], actual: [%s]", test.input, test.expected, actual)
+		}
+		// if we expect an error and there isn't one
+		if test.expectErr && actualErr == nil {
+			t.Errorf("Format(%s): expected an error, but error is nil", test.input)
+		}
+		// if we don't expect an error and there is one
+		if !test.expectErr && actualErr != nil {
+			t.Errorf("Format(%s): expected no error, but error is: %s", test.input, actualErr)
+		}
+	}
+}
+
+func BenchmarkFormat(b *testing.B) {
+	b.StopTimer()
+	for _, test := range areaCodeTests {
+		b.StartTimer()
+		for i := 0; i < b.N; i++ {
+			Format(test.input)
+		}
+		b.StopTimer()
+	}
+}

go/phone-number/phonenumber.go

@@ -0,0 +1,44 @@
+package phonenumber
+
+import (
+	"errors"
+	"strings"
+)
+
+// Number takes a number and validates it
+func Number(num string) (string, error) {
+	num = strings.Map(func(r rune) rune {
+		if r >= '0' && r <= '9' {
+			return r
+		}
+		return -1
+	}, num)
+	// A number can be 11 digits long, if it starts with a 1
+	// but ignore that one.
+	if len(num) == 11 && num[0] == '1' {
+		num = num[1:]
+	}
+	if len(num) != 10 {
+		return "", errors.New("Invalid Number")
+	}
+	return num, nil
+}
+
+// AreaCode takes a number, validates it, and returns the area code
+func AreaCode(num string) (string, error) {
+	num, err := Number(num)
+	if err != nil {
+		return "", err
+	}
+	return num[:3], nil
+}
+
+// Format takes a number, validates it and returns it in the format
+// (nnn) nnn-nnnn
+func Format(num string) (string, error) {
+	num, err := Number(num)
+	if err != nil {
+		return "", err
+	}
+	return "(" + num[:3] + ") " + num[3:6] + "-" + num[6:], nil
+}

go/pig-latin/README.md

@@ -0,0 +1,36 @@
+# Pig Latin
+
+Implement a program that translates from English to Pig Latin
+
+Pig Latin is a made-up children's language that's intended to be
+confusing. It obeys a few simple rules (below), but when it's spoken
+quickly it's really difficult for non-children (and non-native speakers)
+to understand.
+
+- **Rule 1**: If a word begins with a vowel sound, add an "ay" sound to
+  the end of the word.
+- **Rule 2**: If a word begins with a consonant sound, move it to the
+  end of the word, and then add an "ay" sound to the end of the word.
+
+There are a few more rules for edge cases, and there are regional
+variants too.
+
+See <http://en.wikipedia.org/wiki/Pig_latin> for more details.
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+The Pig Latin exercise at Test First Teaching by Ultrasaurus [https://github.com/ultrasaurus/test-first-teaching/blob/master/learn_ruby/pig_latin/](https://github.com/ultrasaurus/test-first-teaching/blob/master/learn_ruby/pig_latin/)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/pig-latin/igpay.go

@@ -0,0 +1,41 @@
+package igpay
+
+import "strings"
+
+// PigLatin takes some words and converts them to pig latin
+// 1) Move starting consonant sounds to the end of the word
+// 2) add 'ay'
+func PigLatin(in string) string {
+	var ret string
+	words := strings.Split(in, " ")
+	for i := range words {
+		ret += pigLatinWord(words[i])
+		if i < len(words)-1 {
+			ret += " "
+		}
+	}
+	return ret
+}
+
+// pigLatinWord actually does the heavy lifting
+func pigLatinWord(in string) string {
+	var ret string
+	// First move all consonant sounds to the end
+	for i := 0; i < len(in); i++ {
+		// Edge consonant sound cases
+		if in[0] == 'q' && in[1] == 'u' {
+			in = in[2:] + string(in[0]) + string(in[1])
+		}
+
+		vowelPos := strings.IndexAny(in, "aeiou")
+
+		// If we have a y and another vowel, then y is a consonant
+		// also, x
+		if vowelPos == 0 || (vowelPos > 1 && (in[0] == 'y' || in[0] == 'x')) {
+			return in + "ay"
+		}
+		in = in[1:] + string(in[0])
+	}
+
+	return ret
+}

go/pig-latin/pig_latin_test.go

@@ -0,0 +1,29 @@
+package igpay
+
+import "testing"
+
+var tests = []struct{ pl, in string }{
+	{"appleay", "apple"},
+	{"earay", "ear"},
+	{"igpay", "pig"},
+	{"oalakay", "koala"},
+	{"airchay", "chair"},
+	{"eenquay", "queen"},
+	{"aresquay", "square"},
+	{"erapythay", "therapy"},
+	{"ushthray", "thrush"},
+	{"oolschay", "school"},
+	{"ickquay astfay unray", "quick fast run"},
+	{"ellowyay", "yellow"},
+	{"yttriaay", "yttria"},
+	{"enonxay", "xenon"},
+	{"xrayay", "xray"},
+}
+
+func TestPigLatin(t *testing.T) {
+	for _, test := range tests {
+		if pl := PigLatin(test.in); pl != test.pl {
+			t.Fatalf("PigLatin(%q) = %q, want %q.", test.in, pl, test.pl)
+		}
+	}
+}

go/prime-factors/README.md

@@ -0,0 +1,48 @@
+# Prime Factors
+
+Compute the prime factors of a given natural number.
+
+A prime number is only evenly divisible by itself and 1.
+
+Note that 1 is not a prime number.
+
+## Example
+
+What are the prime factors of 60?
+
+- Our first divisor is 2. 2 goes into 60, leaving 30.
+- 2 goes into 30, leaving 15.
+  - 2 doesn't go cleanly into 15. So let's move on to our next divisor, 3.
+- 3 goes cleanly into 15, leaving 5.
+  - 3 does not go cleanly into 5. The next possible factor is 4.
+  - 4 does not go cleanly into 5. The next possible factor is 5.
+- 5 does go cleanly into 5.
+- We're left only with 1, so now, we're done.
+
+Our successful divisors in that computation represent the list of prime
+factors of 60: 2, 2, 3, and 5.
+
+You can check this yourself:
+
+- 2 * 2 * 3 * 5
+- = 4 * 15
+- = 60
+- Success!
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+The Prime Factors Kata by Uncle Bob [http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata](http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/prime-factors/prime.go

@@ -0,0 +1,21 @@
+package prime
+
+const testVersion = 2
+
+func Factors(fnd int64) []int64 {
+	var ret []int64
+	var i int64
+	foundFactor := true
+	for i = 2; i < fnd; i++ {
+		for j := range ret {
+			if i%ret[j] == 0 {
+				//  Already covered this case, move on
+				foundFactor = false
+			}
+			if !foundFactor {
+				break
+			}
+		}
+	}
+	return ret
+}

go/prime-factors/primefactors_test.go

@@ -0,0 +1,48 @@
+package prime
+
+// Return prime factors in increasing order
+
+import (
+	"reflect"
+	"testing"
+)
+
+const targetTestVersion = 2
+
+var tests = []struct {
+	input    int64
+	expected []int64
+}{
+	{1, []int64{}},
+	{2, []int64{2}},
+	{3, []int64{3}},
+	{4, []int64{2, 2}},
+	{6, []int64{2, 3}},
+	{8, []int64{2, 2, 2}},
+	{9, []int64{3, 3}},
+	{27, []int64{3, 3, 3}},
+	{625, []int64{5, 5, 5, 5}},
+	{901255, []int64{5, 17, 23, 461}},
+	{93819012551, []int64{11, 9539, 894119}},
+}
+
+func TestPrimeFactors(t *testing.T) {
+	if testVersion != targetTestVersion {
+		t.Fatalf("Found testVersion = %v, want %v", testVersion, targetTestVersion)
+	}
+	for _, test := range tests {
+		actual := Factors(test.input)
+		if !reflect.DeepEqual(actual, test.expected) {
+			t.Errorf("prime.Factors(%d) = %v; expected %v",
+				test.input, actual, test.expected)
+		}
+	}
+}
+
+func BenchmarkPrimeFactors(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range tests {
+			Factors(test.input)
+		}
+	}
+}

go/strain/README.md

@@ -0,0 +1,53 @@
+# Strain
+
+Implement the `keep` and `discard` operation on collections. Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.
+
+Write two functions that each take a function and a list.  One of them will
+return the list of items for which the passed in function is true, and the
+other will return the items for which it is false.
+
+For example, given the collection of numbers:
+
+- 1, 2, 3, 4, 5
+
+And the predicate:
+
+- is the number even?
+
+Then your keep operation should produce:
+
+- 2, 4
+
+While your discard operation should produce:
+
+- 1, 3, 5
+
+Note that the union of keep and discard is all the elements.
+
+The functions may be called `keep` and `discard`, or they may need different
+names in order to not clash with existing functions or concepts in your
+language.
+
+## Restrictions
+
+Keep your hands off that filter/reject/whatchamacallit functionality
+provided by your standard library!  Solve this one yourself using other
+basic tools instead.
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+Conversation with James Edward Gray II [https://twitter.com/jeg2](https://twitter.com/jeg2)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

go/strain/strain.go

@@ -0,0 +1,54 @@
+package strain
+
+// Ints is a slice of int
+type Ints []int
+
+// Lists is a slice of int slices
+type Lists [][]int
+
+// Strings is a slice of strings
+type Strings []string
+
+// Keep runs the Ints through a function and returns the ones that succeed
+func (i Ints) Keep(kf func(int) bool) Ints {
+	var ret Ints
+	for idx := range i {
+		if kf(i[idx]) {
+			ret = append(ret, i[idx])
+		}
+	}
+	return ret
+}
+
+// Discard runs the Ints through a function and returns the ones that fail
+func (i Ints) Discard(df func(int) bool) Ints {
+	var ret Ints
+	for idx := range i {
+		if !df(i[idx]) {
+			ret = append(ret, i[idx])
+		}
+	}
+	return ret
+}
+
+// Keep runs the Lists through a function and returns the ones that succeed
+func (l Lists) Keep(kf func([]int) bool) Lists {
+	var ret Lists
+	for idx := range l {
+		if kf(l[idx]) {
+			ret = append(ret, l[idx])
+		}
+	}
+	return ret
+}
+
+// Keep runs the Strings through a function and returns the ones that succeed
+func (s Strings) Keep(kf func(string) bool) Strings {
+	var ret Strings
+	for idx := range s {
+		if kf(s[idx]) {
+			ret = append(ret, s[idx])
+		}
+	}
+	return ret
+}

go/strain/strain_test.go

@@ -0,0 +1,170 @@
+// Collections, hm?  For this exercise in Go you'll work with slices as
+// collections.  Define the following in your solution:
+//
+//    type Ints []int
+//    type Lists [][]int
+//    type Strings []string
+//
+// Then complete the exercise by implementing these methods:
+//
+//    (Ints) Keep(func(int) bool) Ints
+//    (Ints) Discard(func(int) bool) Ints
+//    (Lists) Keep(func([]int) bool) Lists
+//    (Strings) Keep(func(string) bool) Strings
+
+package strain
+
+import (
+	"reflect"
+	"testing"
+)
+
+func lt10(x int) bool { return x < 10 }
+func gt10(x int) bool { return x > 10 }
+func odd(x int) bool  { return x&1 == 1 }
+func even(x int) bool { return x&1 == 0 }
+
+var keepTests = []struct {
+	pred func(int) bool
+	list Ints
+	want Ints
+}{
+	{lt10,
+		nil,
+		nil},
+	{lt10,
+		Ints{1, 2, 3},
+		Ints{1, 2, 3}},
+	{odd,
+		Ints{1, 2, 3},
+		Ints{1, 3}},
+	{even,
+		Ints{1, 2, 3, 4, 5},
+		Ints{2, 4}},
+}
+
+func TestKeepInts(t *testing.T) {
+	for _, test := range keepTests {
+		// setup here copies test.list, preserving the nil value if it is nil
+		// and making a fresh copy of the underlying array otherwise.
+		cp := test.list
+		if cp != nil {
+			cp = append(Ints{}, cp...)
+		}
+		switch res := cp.Keep(test.pred); {
+		case !reflect.DeepEqual(cp, test.list):
+			t.Fatalf("Ints%v.Keep() should not modify its reciever.  "+
+				"Found %v, reciever should stay %v",
+				test.list, cp, test.list)
+		case !reflect.DeepEqual(res, test.want):
+			t.Fatalf("Ints%v.Keep() = %v, want %v",
+				test.list, res, test.want)
+		}
+	}
+}
+
+var discardTests = []struct {
+	pred func(int) bool
+	list Ints
+	want Ints
+}{
+	{lt10,
+		nil,
+		nil},
+	{gt10,
+		Ints{1, 2, 3},
+		Ints{1, 2, 3}},
+	{odd,
+		Ints{1, 2, 3},
+		Ints{2}},
+	{even,
+		Ints{1, 2, 3, 4, 5},
+		Ints{1, 3, 5}},
+}
+
+func TestDiscardInts(t *testing.T) {
+	for _, test := range discardTests {
+		cp := test.list
+		if cp != nil {
+			cp = append(Ints{}, cp...) // dup underlying array
+		}
+		switch res := cp.Discard(test.pred); {
+		case !reflect.DeepEqual(cp, test.list):
+			t.Fatalf("Ints%v.Discard() should not modify its reciever.  "+
+				"Found %v, reciever should stay %v",
+				test.list, cp, test.list)
+		case !reflect.DeepEqual(res, test.want):
+			t.Fatalf("Ints%v.Discard() = %v, want %v",
+				test.list, res, test.want)
+		}
+	}
+}
+
+func TestKeepStrings(t *testing.T) {
+	zword := func(s string) bool { return len(s) > 0 && s[0] == 'z' }
+	list := Strings{"apple", "zebra", "banana", "zombies", "cherimoya", "zelot"}
+	want := Strings{"zebra", "zombies", "zelot"}
+
+	cp := append(Strings{}, list...) // make copy, as with TestInts
+	switch res := cp.Keep(zword); {
+	case !reflect.DeepEqual(cp, list):
+		t.Fatalf("Strings%v.Keep() should not modify its reciever.  "+
+			"Found %v, reciever should stay %v",
+			list, cp, list)
+	case !reflect.DeepEqual(res, want):
+		t.Fatalf("Strings%v.Keep() = %v, want %v",
+			list, res, want)
+	}
+}
+
+func TestKeepLists(t *testing.T) {
+	has5 := func(l []int) bool {
+		for _, e := range l {
+			if e == 5 {
+				return true
+			}
+		}
+		return false
+	}
+	list := Lists{
+		{1, 2, 3},
+		{5, 5, 5},
+		{5, 1, 2},
+		{2, 1, 2},
+		{1, 5, 2},
+		{2, 2, 1},
+		{1, 2, 5},
+	}
+	want := Lists{
+		{5, 5, 5},
+		{5, 1, 2},
+		{1, 5, 2},
+		{1, 2, 5},
+	}
+	cp := append(Lists{}, list...)
+	switch res := cp.Keep(has5); {
+	case !reflect.DeepEqual(cp, list):
+		t.Fatalf("Lists%v.Keep() should not modify its reciever.  "+
+			"Found %v, reciever should stay %v",
+			list, cp, list)
+	case !reflect.DeepEqual(res, want):
+		t.Fatalf("Lists%v.Keep() = %v, want %v",
+			list, res, want)
+	}
+}
+
+func BenchmarkKeepInts(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range keepTests {
+			test.list.Keep(test.pred)
+		}
+	}
+}
+
+func BenchmarkDiscardInts(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range discardTests {
+			test.list.Discard(test.pred)
+		}
+	}
+}