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pawelo091991's solution

to Food Chain in the C++ Track

Published at Sep 09 2019 · 0 comments
Instructions
Test suite
Solution

Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.

While you could copy/paste the lyrics, or read them from a file, this problem is much more interesting if you approach it algorithmically.

This is a cumulative song of unknown origin.

This is one of many common variants.

I know an old lady who swallowed a fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a spider.
It wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a bird.
How absurd to swallow a bird!
She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a cat.
Imagine that, to swallow a cat!
She swallowed the cat to catch the bird.
She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a dog.
What a hog, to swallow a dog!
She swallowed the dog to catch the cat.
She swallowed the cat to catch the bird.
She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a goat.
Just opened her throat and swallowed a goat!
She swallowed the goat to catch the dog.
She swallowed the dog to catch the cat.
She swallowed the cat to catch the bird.
She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a cow.
I don't know how she swallowed a cow!
She swallowed the cow to catch the goat.
She swallowed the goat to catch the dog.
She swallowed the dog to catch the cat.
She swallowed the cat to catch the bird.
She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
She swallowed the spider to catch the fly.
I don't know why she swallowed the fly. Perhaps she'll die.

I know an old lady who swallowed a horse.
She's dead, of course!

Getting Started

Make sure you have read the Installing and Running the Tests pages for C++ on exercism.io. This covers the basic information on setting up the development environment expected by the exercises.

Passing the Tests

Get the first test compiling, linking and passing by following the three rules of test-driven development. Create just enough structure by declaring namespaces, functions, classes, etc., to satisfy any compiler errors and get the test to fail. Then write just enough code to get the test to pass. Once you've done that, uncomment the next test by moving the following line past the next test.

#if defined(EXERCISM_RUN_ALL_TESTS)

This may result in compile errors as new constructs may be invoked that you haven't yet declared or defined. Again, fix the compile errors minimally to get a failing test, then change the code minimally to pass the test, refactor your implementation for readability and expressiveness and then go on to the next test.

Try to use standard C++11 facilities in preference to writing your own low-level algorithms or facilities by hand. CppReference is a wiki reference to the C++ language and standard library. If you are new to C++, but have programmed in C, beware of C traps and pitfalls.

Source

Wikipedia http://en.wikipedia.org/wiki/There_Was_an_Old_Lady_Who_Swallowed_a_Fly

Submitting Incomplete Solutions

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

food_chain_test.cpp

#include "food_chain.h"
#include "test/catch.hpp"

using namespace std;

TEST_CASE("fly")
{
    string expected = "I know an old lady who swallowed a fly.\n"
        "I don't know why she swallowed the fly. Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(1));
}

#if defined(EXERCISM_RUN_ALL_TESTS)
TEST_CASE("spider")
{
    string expected = "I know an old lady who swallowed a spider.\n"
        "It wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(2));
}

TEST_CASE("bird")
{
    string expected = "I know an old lady who swallowed a bird.\n"
        "How absurd to swallow a bird!\n"
        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(3));
}

TEST_CASE("cat")
{
    string expected = "I know an old lady who swallowed a cat.\n"
        "Imagine that, to swallow a cat!\n"
        "She swallowed the cat to catch the bird.\n"
        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. "
        "Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(4));
}

TEST_CASE("dog")
{
    string expected = "I know an old lady who swallowed a dog.\n"
        "What a hog, to swallow a dog!\n"
        "She swallowed the dog to catch the cat.\n"
        "She swallowed the cat to catch the bird.\n"
        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. "
        "Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(5));
}

TEST_CASE("goat")
{
    string expected = "I know an old lady who swallowed a goat.\n"
        "Just opened her throat and swallowed a goat!\n"
        "She swallowed the goat to catch the dog.\n"
        "She swallowed the dog to catch the cat.\n"
        "She swallowed the cat to catch the bird.\n"
        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. "
        "Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(6));
}

TEST_CASE("cow")
{
    string expected = "I know an old lady who swallowed a cow.\n"
        "I don't know how she swallowed a cow!\n"
        "She swallowed the cow to catch the goat.\n"
        "She swallowed the goat to catch the dog.\n"
        "She swallowed the dog to catch the cat.\n"
        "She swallowed the cat to catch the bird.\n"
        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. "
        "Perhaps she'll die.\n";

    REQUIRE(expected == food_chain::verse(7));
}

TEST_CASE("horse")
{
    string expected = "I know an old lady who swallowed a horse.\n"
        "She's dead, of course!\n";

    REQUIRE(expected == food_chain::verse(8));
}

TEST_CASE("multiple_verses")
{
    string expected = 
        "I know an old lady who swallowed a fly.\n"
        "I don't know why she swallowed the fly. Perhaps she'll die.\n"
        "\n"
        "I know an old lady who swallowed a spider.\n"
        "It wriggled and jiggled and tickled inside her.\n"
        "She swallowed the spider to catch the fly.\n"
        "I don't know why she swallowed the fly. Perhaps she'll die.\n"
        "\n";

    REQUIRE(expected == food_chain::verses(1, 2));
}

TEST_CASE("the_whole_song")
{
    REQUIRE(food_chain::verses(1, 8) == food_chain::sing());
}
#endif

food_chain.h

#ifndef FOOD_CHAIN
#define FOOD_CHAIN
#include <string>
#include <utility>

namespace food_chain {
	std::string verse(uint16_t);
	std::string verses(uint16_t, uint16_t);
	std::string sing();
}
#endif // !FOOD_CHAIN

food_chain.cpp

#include "food_chain.h"

std::string food_chain::verse(uint16_t num) {
	
	std::string verse;
	switch (num) {
	case 1:
		verse = "I know an old lady who swallowed a fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 2:
		verse = "I know an old lady who swallowed a spider.\n"
			"It wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 3:
		verse = "I know an old lady who swallowed a bird.\n"
			"How absurd to swallow a bird!\n"
			"She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 4:
		verse = "I know an old lady who swallowed a cat.\n"
			"Imagine that, to swallow a cat!\n"
			"She swallowed the cat to catch the bird.\n"
			"She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 5:
		verse = "I know an old lady who swallowed a dog.\n"
			"What a hog, to swallow a dog!\n"
			"She swallowed the dog to catch the cat.\n"
			"She swallowed the cat to catch the bird.\n"
			"She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 6:
		verse = "I know an old lady who swallowed a goat.\n"
			"Just opened her throat and swallowed a goat!\n"
			"She swallowed the goat to catch the dog.\n"
			"She swallowed the dog to catch the cat.\n"
			"She swallowed the cat to catch the bird.\n"
			"She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 7:
		verse = "I know an old lady who swallowed a cow.\n"
			"I don't know how she swallowed a cow!\n"
			"She swallowed the cow to catch the goat.\n"
			"She swallowed the goat to catch the dog.\n"
			"She swallowed the dog to catch the cat.\n"
			"She swallowed the cat to catch the bird.\n"
			"She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.\n"
			"She swallowed the spider to catch the fly.\n"
			"I don't know why she swallowed the fly. Perhaps she'll die.\n";
		break;
	case 8:
		verse = "I know an old lady who swallowed a horse.\n"
			"She's dead, of course!\n";
	}
	return verse;
}

std::string food_chain::verses(uint16_t start, uint16_t end) {
	std::string song = "";
	for (int i = start; i <= end; i++)
		song += verse(i) + '\n';

	return song;
}

std::string food_chain::sing() {
	return verses(1, 8);
}

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