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vlzware's solution

to Beer Song in the C Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Recite the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.

Note that not all verses are identical.

99 bottles of beer on the wall, 99 bottles of beer.
Take one down and pass it around, 98 bottles of beer on the wall.

98 bottles of beer on the wall, 98 bottles of beer.
Take one down and pass it around, 97 bottles of beer on the wall.

97 bottles of beer on the wall, 97 bottles of beer.
Take one down and pass it around, 96 bottles of beer on the wall.

96 bottles of beer on the wall, 96 bottles of beer.
Take one down and pass it around, 95 bottles of beer on the wall.

95 bottles of beer on the wall, 95 bottles of beer.
Take one down and pass it around, 94 bottles of beer on the wall.

94 bottles of beer on the wall, 94 bottles of beer.
Take one down and pass it around, 93 bottles of beer on the wall.

93 bottles of beer on the wall, 93 bottles of beer.
Take one down and pass it around, 92 bottles of beer on the wall.

92 bottles of beer on the wall, 92 bottles of beer.
Take one down and pass it around, 91 bottles of beer on the wall.

91 bottles of beer on the wall, 91 bottles of beer.
Take one down and pass it around, 90 bottles of beer on the wall.

90 bottles of beer on the wall, 90 bottles of beer.
Take one down and pass it around, 89 bottles of beer on the wall.

89 bottles of beer on the wall, 89 bottles of beer.
Take one down and pass it around, 88 bottles of beer on the wall.

88 bottles of beer on the wall, 88 bottles of beer.
Take one down and pass it around, 87 bottles of beer on the wall.

87 bottles of beer on the wall, 87 bottles of beer.
Take one down and pass it around, 86 bottles of beer on the wall.

86 bottles of beer on the wall, 86 bottles of beer.
Take one down and pass it around, 85 bottles of beer on the wall.

85 bottles of beer on the wall, 85 bottles of beer.
Take one down and pass it around, 84 bottles of beer on the wall.

84 bottles of beer on the wall, 84 bottles of beer.
Take one down and pass it around, 83 bottles of beer on the wall.

83 bottles of beer on the wall, 83 bottles of beer.
Take one down and pass it around, 82 bottles of beer on the wall.

82 bottles of beer on the wall, 82 bottles of beer.
Take one down and pass it around, 81 bottles of beer on the wall.

81 bottles of beer on the wall, 81 bottles of beer.
Take one down and pass it around, 80 bottles of beer on the wall.

80 bottles of beer on the wall, 80 bottles of beer.
Take one down and pass it around, 79 bottles of beer on the wall.

79 bottles of beer on the wall, 79 bottles of beer.
Take one down and pass it around, 78 bottles of beer on the wall.

78 bottles of beer on the wall, 78 bottles of beer.
Take one down and pass it around, 77 bottles of beer on the wall.

77 bottles of beer on the wall, 77 bottles of beer.
Take one down and pass it around, 76 bottles of beer on the wall.

76 bottles of beer on the wall, 76 bottles of beer.
Take one down and pass it around, 75 bottles of beer on the wall.

75 bottles of beer on the wall, 75 bottles of beer.
Take one down and pass it around, 74 bottles of beer on the wall.

74 bottles of beer on the wall, 74 bottles of beer.
Take one down and pass it around, 73 bottles of beer on the wall.

73 bottles of beer on the wall, 73 bottles of beer.
Take one down and pass it around, 72 bottles of beer on the wall.

72 bottles of beer on the wall, 72 bottles of beer.
Take one down and pass it around, 71 bottles of beer on the wall.

71 bottles of beer on the wall, 71 bottles of beer.
Take one down and pass it around, 70 bottles of beer on the wall.

70 bottles of beer on the wall, 70 bottles of beer.
Take one down and pass it around, 69 bottles of beer on the wall.

69 bottles of beer on the wall, 69 bottles of beer.
Take one down and pass it around, 68 bottles of beer on the wall.

68 bottles of beer on the wall, 68 bottles of beer.
Take one down and pass it around, 67 bottles of beer on the wall.

67 bottles of beer on the wall, 67 bottles of beer.
Take one down and pass it around, 66 bottles of beer on the wall.

66 bottles of beer on the wall, 66 bottles of beer.
Take one down and pass it around, 65 bottles of beer on the wall.

65 bottles of beer on the wall, 65 bottles of beer.
Take one down and pass it around, 64 bottles of beer on the wall.

64 bottles of beer on the wall, 64 bottles of beer.
Take one down and pass it around, 63 bottles of beer on the wall.

63 bottles of beer on the wall, 63 bottles of beer.
Take one down and pass it around, 62 bottles of beer on the wall.

62 bottles of beer on the wall, 62 bottles of beer.
Take one down and pass it around, 61 bottles of beer on the wall.

61 bottles of beer on the wall, 61 bottles of beer.
Take one down and pass it around, 60 bottles of beer on the wall.

60 bottles of beer on the wall, 60 bottles of beer.
Take one down and pass it around, 59 bottles of beer on the wall.

59 bottles of beer on the wall, 59 bottles of beer.
Take one down and pass it around, 58 bottles of beer on the wall.

58 bottles of beer on the wall, 58 bottles of beer.
Take one down and pass it around, 57 bottles of beer on the wall.

57 bottles of beer on the wall, 57 bottles of beer.
Take one down and pass it around, 56 bottles of beer on the wall.

56 bottles of beer on the wall, 56 bottles of beer.
Take one down and pass it around, 55 bottles of beer on the wall.

55 bottles of beer on the wall, 55 bottles of beer.
Take one down and pass it around, 54 bottles of beer on the wall.

54 bottles of beer on the wall, 54 bottles of beer.
Take one down and pass it around, 53 bottles of beer on the wall.

53 bottles of beer on the wall, 53 bottles of beer.
Take one down and pass it around, 52 bottles of beer on the wall.

52 bottles of beer on the wall, 52 bottles of beer.
Take one down and pass it around, 51 bottles of beer on the wall.

51 bottles of beer on the wall, 51 bottles of beer.
Take one down and pass it around, 50 bottles of beer on the wall.

50 bottles of beer on the wall, 50 bottles of beer.
Take one down and pass it around, 49 bottles of beer on the wall.

49 bottles of beer on the wall, 49 bottles of beer.
Take one down and pass it around, 48 bottles of beer on the wall.

48 bottles of beer on the wall, 48 bottles of beer.
Take one down and pass it around, 47 bottles of beer on the wall.

47 bottles of beer on the wall, 47 bottles of beer.
Take one down and pass it around, 46 bottles of beer on the wall.

46 bottles of beer on the wall, 46 bottles of beer.
Take one down and pass it around, 45 bottles of beer on the wall.

45 bottles of beer on the wall, 45 bottles of beer.
Take one down and pass it around, 44 bottles of beer on the wall.

44 bottles of beer on the wall, 44 bottles of beer.
Take one down and pass it around, 43 bottles of beer on the wall.

43 bottles of beer on the wall, 43 bottles of beer.
Take one down and pass it around, 42 bottles of beer on the wall.

42 bottles of beer on the wall, 42 bottles of beer.
Take one down and pass it around, 41 bottles of beer on the wall.

41 bottles of beer on the wall, 41 bottles of beer.
Take one down and pass it around, 40 bottles of beer on the wall.

40 bottles of beer on the wall, 40 bottles of beer.
Take one down and pass it around, 39 bottles of beer on the wall.

39 bottles of beer on the wall, 39 bottles of beer.
Take one down and pass it around, 38 bottles of beer on the wall.

38 bottles of beer on the wall, 38 bottles of beer.
Take one down and pass it around, 37 bottles of beer on the wall.

37 bottles of beer on the wall, 37 bottles of beer.
Take one down and pass it around, 36 bottles of beer on the wall.

36 bottles of beer on the wall, 36 bottles of beer.
Take one down and pass it around, 35 bottles of beer on the wall.

35 bottles of beer on the wall, 35 bottles of beer.
Take one down and pass it around, 34 bottles of beer on the wall.

34 bottles of beer on the wall, 34 bottles of beer.
Take one down and pass it around, 33 bottles of beer on the wall.

33 bottles of beer on the wall, 33 bottles of beer.
Take one down and pass it around, 32 bottles of beer on the wall.

32 bottles of beer on the wall, 32 bottles of beer.
Take one down and pass it around, 31 bottles of beer on the wall.

31 bottles of beer on the wall, 31 bottles of beer.
Take one down and pass it around, 30 bottles of beer on the wall.

30 bottles of beer on the wall, 30 bottles of beer.
Take one down and pass it around, 29 bottles of beer on the wall.

29 bottles of beer on the wall, 29 bottles of beer.
Take one down and pass it around, 28 bottles of beer on the wall.

28 bottles of beer on the wall, 28 bottles of beer.
Take one down and pass it around, 27 bottles of beer on the wall.

27 bottles of beer on the wall, 27 bottles of beer.
Take one down and pass it around, 26 bottles of beer on the wall.

26 bottles of beer on the wall, 26 bottles of beer.
Take one down and pass it around, 25 bottles of beer on the wall.

25 bottles of beer on the wall, 25 bottles of beer.
Take one down and pass it around, 24 bottles of beer on the wall.

24 bottles of beer on the wall, 24 bottles of beer.
Take one down and pass it around, 23 bottles of beer on the wall.

23 bottles of beer on the wall, 23 bottles of beer.
Take one down and pass it around, 22 bottles of beer on the wall.

22 bottles of beer on the wall, 22 bottles of beer.
Take one down and pass it around, 21 bottles of beer on the wall.

21 bottles of beer on the wall, 21 bottles of beer.
Take one down and pass it around, 20 bottles of beer on the wall.

20 bottles of beer on the wall, 20 bottles of beer.
Take one down and pass it around, 19 bottles of beer on the wall.

19 bottles of beer on the wall, 19 bottles of beer.
Take one down and pass it around, 18 bottles of beer on the wall.

18 bottles of beer on the wall, 18 bottles of beer.
Take one down and pass it around, 17 bottles of beer on the wall.

17 bottles of beer on the wall, 17 bottles of beer.
Take one down and pass it around, 16 bottles of beer on the wall.

16 bottles of beer on the wall, 16 bottles of beer.
Take one down and pass it around, 15 bottles of beer on the wall.

15 bottles of beer on the wall, 15 bottles of beer.
Take one down and pass it around, 14 bottles of beer on the wall.

14 bottles of beer on the wall, 14 bottles of beer.
Take one down and pass it around, 13 bottles of beer on the wall.

13 bottles of beer on the wall, 13 bottles of beer.
Take one down and pass it around, 12 bottles of beer on the wall.

12 bottles of beer on the wall, 12 bottles of beer.
Take one down and pass it around, 11 bottles of beer on the wall.

11 bottles of beer on the wall, 11 bottles of beer.
Take one down and pass it around, 10 bottles of beer on the wall.

10 bottles of beer on the wall, 10 bottles of beer.
Take one down and pass it around, 9 bottles of beer on the wall.

9 bottles of beer on the wall, 9 bottles of beer.
Take one down and pass it around, 8 bottles of beer on the wall.

8 bottles of beer on the wall, 8 bottles of beer.
Take one down and pass it around, 7 bottles of beer on the wall.

7 bottles of beer on the wall, 7 bottles of beer.
Take one down and pass it around, 6 bottles of beer on the wall.

6 bottles of beer on the wall, 6 bottles of beer.
Take one down and pass it around, 5 bottles of beer on the wall.

5 bottles of beer on the wall, 5 bottles of beer.
Take one down and pass it around, 4 bottles of beer on the wall.

4 bottles of beer on the wall, 4 bottles of beer.
Take one down and pass it around, 3 bottles of beer on the wall.

3 bottles of beer on the wall, 3 bottles of beer.
Take one down and pass it around, 2 bottles of beer on the wall.

2 bottles of beer on the wall, 2 bottles of beer.
Take one down and pass it around, 1 bottle of beer on the wall.

1 bottle of beer on the wall, 1 bottle of beer.
Take it down and pass it around, no more bottles of beer on the wall.

No more bottles of beer on the wall, no more bottles of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.

For bonus points

Did you get the tests passing and the code clean? If you want to, these are some additional things you could try:

  • Remove as much duplication as you possibly can.
  • Optimize for readability, even if it means introducing duplication.
  • If you've removed all the duplication, do you have a lot of conditionals? Try replacing the conditionals with polymorphism, if it applies in this language. How readable is it?

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

Getting Started

Make sure you have read the C page on the Exercism site. 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.

The included makefile can be used to create and run the tests using the test task.

make test

Create just the functions you need 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, move onto the next test.

As you progress through the tests, take the time to refactor your implementation for readability and expressiveness and then go on to the next test.

Try to use standard C99 facilities in preference to writing your own low-level algorithms or facilities by hand.

Source

Learn to Program by Chris Pine http://pine.fm/LearnToProgram/?Chapter=06

Submitting Incomplete Solutions

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

test_beer_song.c

#include "vendor/unity.h"
#include "../src/beer_song.h"

#define BUFFER_SIZE   (1024)

void setUp(void)
{
}

void tearDown(void)
{
}

void test_handles_arbitrary_verse(void)
{
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "84 bottles of beer on the wall, 84 bottles of beer.\n"
       "Take one down and pass it around, 83 bottles of beer on the wall.\n";

   verse(response, 84);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

void test_handles_2_bottles(void)
{
   TEST_IGNORE();               // delete this line to run test
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "2 bottles of beer on the wall, 2 bottles of beer.\n"
       "Take one down and pass it around, 1 bottle of beer on the wall.\n";

   verse(response, 2);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

void test_handles_1_bottle(void)
{
   TEST_IGNORE();
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "1 bottle of beer on the wall, 1 bottle of beer.\n"
       "Take it down and pass it around, no more bottles of beer on the wall.\n";

   verse(response, 1);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

void test_handles_0_bottles(void)
{
   TEST_IGNORE();
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "No more bottles of beer on the wall, no more bottles of beer.\n"
       "Go to the store and buy some more, 99 bottles of beer on the wall.\n";

   verse(response, 0);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

void test_sings_several_verses(void)
{
   TEST_IGNORE();
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "8 bottles of beer on the wall, 8 bottles of beer.\n"
       "Take one down and pass it around, 7 bottles of beer on the wall.\n"
       "\n"
       "7 bottles of beer on the wall, 7 bottles of beer.\n"
       "Take one down and pass it around, 6 bottles of beer on the wall.\n"
       "\n"
       "6 bottles of beer on the wall, 6 bottles of beer.\n"
       "Take one down and pass it around, 5 bottles of beer on the wall.\n";

   sing(response, 8, 6);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

void test_sings_the_last_4_verses(void)
{
   TEST_IGNORE();
   char response[BUFFER_SIZE];
   const char expected[BUFFER_SIZE] =
       "3 bottles of beer on the wall, 3 bottles of beer.\n"
       "Take one down and pass it around, 2 bottles of beer on the wall.\n"
       "\n"
       "2 bottles of beer on the wall, 2 bottles of beer.\n"
       "Take one down and pass it around, 1 bottle of beer on the wall.\n"
       "\n"
       "1 bottle of beer on the wall, 1 bottle of beer.\n"
       "Take it down and pass it around, no more bottles of beer on the wall.\n"
       "\n"
       "No more bottles of beer on the wall, no more bottles of beer.\n"
       "Go to the store and buy some more, 99 bottles of beer on the wall.\n";

   sing(response, 3, 0);
   TEST_ASSERT_EQUAL_STRING(expected, response);
}

int main(void)
{
   UnityBegin("test/test_beer_song.c");

   RUN_TEST(test_handles_arbitrary_verse);
   RUN_TEST(test_handles_2_bottles);
   RUN_TEST(test_handles_1_bottle);
   RUN_TEST(test_handles_0_bottles);
   RUN_TEST(test_sings_several_verses);
   RUN_TEST(test_sings_the_last_4_verses);

   UnityEnd();
   return 0;
}

src/beer_song.c

#include "beer_song.h"
#include <stdio.h>

const char *bottle = " bottle";
const char *bottles = " bottles";
const char *on_the_wall = " of beer on the wall";
const char *of_beer = " of beer.\n";
const char *take_one = "Take one down and pass it around, ";
const char *take_it = "Take it down and pass it around, ";
const char *no_more = "No more";
const char *no_more_n = "no more";
const char *go_to_store = "Go to the store and buy some more, ";

void mcat(int *pos, char *dst, const char *src_);

void verse(char *buf, int count)
{
	if (count > 99 || count < 0) {
		fprintf(stderr, "Invalid bottle count.\n");
		return;
	}

	int pos = 0;
	char bot_bef[7] = {0};
	char bot_aft[7] = {0};
	if (count == 0)
		sprintf(bot_bef, "%s", no_more);
	else
		sprintf(bot_bef, "%i", count);
	sprintf(bot_aft, "%i", count == 0? 99 : count-1);

	mcat(&pos, buf, count == 0? no_more : bot_bef);
	mcat(&pos, buf, count == 1? bottle : bottles);
	mcat(&pos, buf, on_the_wall);
	mcat(&pos, buf, ", ");
	mcat(&pos, buf, count == 0? no_more_n : bot_bef);
	mcat(&pos, buf, count == 1? bottle : bottles);
	mcat(&pos, buf, of_beer);
	mcat(&pos, buf, count == 0? go_to_store :
		count == 1? take_it : take_one);
	mcat(&pos, buf, count == 1? no_more_n : bot_aft);
	mcat(&pos, buf, count == 2? bottle : bottles);
	mcat(&pos, buf, on_the_wall);
	mcat(&pos, buf, ".\n");
}

void sing(char *buf, int from, int to)
{
	if (to > from)
		return;
	int pos = 0;
	char l_buf[1024];
	for (; from >= to + 1; from--) {
		verse(l_buf, from);
		mcat(&pos, buf, l_buf);
		mcat(&pos, buf, "\n");
	}
	verse(l_buf, from);
	mcat(&pos, buf, l_buf);
}

/**
 * mcat: concatenate strings, puts the new length in pos,
 * assumes dst is big enough
 */
void mcat(int *pos, char *dst, const char *src_)
{
	char *src = (char*) src_;
	char *tmp = dst + *pos;
	while ((*tmp++ = *src++))
		(*pos)++;
	*tmp = '\0';
}

src/beer_song.h

#ifndef BEER_SONG_H
#define BEER_SONG_H

void verse(char *buf, int count);
void sing(char *buf, int from, int to);

#endif

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