Avatar of spinguice

spinguice's solution

to House in the Go Track

Published at Jun 03 2019 · 0 comments
Instructions
Test suite
Solution

Recite the nursery rhyme 'This is the House that Jack Built'.

[The] process of placing a phrase of clause within another phrase of clause is called embedding. It is through the processes of recursion and embedding that we are able to take a finite number of forms (words and phrases) and construct an infinite number of expressions. Furthermore, embedding also allows us to construct an infinitely long structure, in theory anyway.

The nursery rhyme reads as follows:

This is the house that Jack built.

This is the malt
that lay in the house that Jack built.

This is the rat
that ate the malt
that lay in the house that Jack built.

This is the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the horse and the hound and the horn
that belonged to the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

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.

Source

British nursery rhyme http://en.wikipedia.org/wiki/This_Is_The_House_That_Jack_Built

Submitting Incomplete Solutions

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

house_test.go

// As ever, there are different ways to complete this exercise.
// Try using using programmatic recursion to generate the verses of the song,
// thus reflecting the song's grammatical recursion.

// While recursion isn't always the simplest or most efficient solution to a problem,
// it's a powerful programming technique nonetheless.
//
// New to recursion? Here's a quick introduction:
// https://www.golang-book.com/books/intro/7#section5

package house

import (
	"strings"
	"testing"
)

var (
	// song copied from README
	expectedSong = `This is the house that Jack built.

This is the malt
that lay in the house that Jack built.

This is the rat
that ate the malt
that lay in the house that Jack built.

This is the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the horse and the hound and the horn
that belonged to the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.`

	expectedVerses = strings.Split(expectedSong, "\n\n")
)

func TestVerse(t *testing.T) {
	for v := 0; v < len(expectedVerses); v++ {
		if ret := Verse(v + 1); ret != expectedVerses[v] {
			t.Fatalf("Verse(%d) =\n%q\n  want:\n%q", v+1, ret, expectedVerses[v])
		}
	}
}

func TestSong(t *testing.T) {
	s := Song()
	if s == expectedSong {
		return
	}
	// a little help in locating an error
	gotStanzas := len(strings.Split(s, "\n\n"))
	wantStanzas := len(expectedVerses)
	if wantStanzas != gotStanzas {
		t.Fatalf("Song() has %d verse(s), want %d verses", gotStanzas, wantStanzas)
	}
	got := strings.Split(s, "\n")
	want := strings.Split(expectedSong, "\n")
	var g, w string
	var i int
	for i, w = range want {
		if len(got) <= i {
			g = ""
			break
		}
		if g = got[i]; g != w {
			break
		}
	}
	t.Fatalf("Song() line %d =\n%q\n want \n%q", i+1, g, w)
}
package house

import "strings"

var verses = []struct {
	verb    string
	subject string
}{
	{"lay in", "house that Jack built"},
	{"ate", "malt"},
	{"killed", "rat"},
	{"worried", "cat"},
	{"tossed", "dog"},
	{"milked", "cow with the crumpled horn"},
	{"kissed", "maiden all forlorn"},
	{"married", "man all tattered and torn"},
	{"woke", "priest all shaven and shorn"},
	{"kept", "rooster that crowed in the morn"},
	{"belonged to", "farmer sowing his corn"},
	{"", "horse and the hound and the horn"},
}

//Verse returns the nth verse of the house song
func Verse(n int) string {
	buf := strings.Builder{}
	index := n - 1

	buf.WriteString("This is the ")
	buf.WriteString(verses[index].subject)

	for i := index - 1; i >= 0; i-- {
		buf.WriteRune('\n')
		buf.WriteString("that ")
		buf.WriteString(verses[i].verb)
		buf.WriteString(" the ")
		buf.WriteString(verses[i].subject)
	}
	buf.WriteRune('.')

	return buf.String()
}

//Song returns all 12 verses of the house song
func Song() string {
	allVerses := make([]string, len(verses))
	for i := range verses {
		allVerses[i] = Verse(i + 1)
	}
	return strings.Join(allVerses, "\n\n")
}

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