99 bottles of beer: Difference between revisions
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=={{header|C++}}== |
=={{header|C++}}== |
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=== The simple solution === |
=== The simple solution === |
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< |
<cpp>#include<iostream> |
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using namespace std; |
using namespace std; |
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int main() { |
int main() { |
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cout << x-1 << " bottles of beer on the wall" << endl << endl; |
cout << x-1 << " bottles of beer on the wall" << endl << endl; |
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} |
} |
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}</ |
}</cpp> |
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=== An object-oriented solution === |
=== An object-oriented solution === |
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{{works with|GCC|4.1.2 20061115 (prerelease) (SUSE Linux)}} |
{{works with|GCC|4.1.2 20061115 (prerelease) (SUSE Linux)}} |
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< |
<cpp>#include <iostream> |
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#include <ostream> |
#include <ostream> |
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#include <string> |
#include <string> |
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bottle_song::song song(100); |
bottle_song::song song(100); |
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song.sing(std::cout); |
song.sing(std::cout); |
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}</ |
}</cpp> |
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=== A template metaprogramming solution === |
=== A template metaprogramming solution === |
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Of course, the output of the program always looks the same. One may therefore question why the program has to do all that tedious subtracting during runtime. Couldn't the compiler just generate the code to output the text, with ready-calculated constants? Indeed, it can, and the technique is called template metaprogramming. The following short code gives the text without containing a single variable, let alone a loop: |
Of course, the output of the program always looks the same. One may therefore question why the program has to do all that tedious subtracting during runtime. Couldn't the compiler just generate the code to output the text, with ready-calculated constants? Indeed, it can, and the technique is called template metaprogramming. The following short code gives the text without containing a single variable, let alone a loop: |
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< |
<cpp>#include <iostream> |
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#include <ostream> |
#include <ostream> |
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{ |
{ |
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bottle_countdown<100, 1>::print(); |
bottle_countdown<100, 1>::print(); |
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}</ |
}</cpp> |
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=== A preprocessor solution === |
=== A preprocessor solution === |
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Of course, with the template metaprogramming solution, the program has still do the conversion of numbers to strings at runtime, and those function calls also cost unnecessary time. Couldn't we just compose the complete text at compile time, and just output it at run time? Well, with the preprocessor, that's indeed possible: |
Of course, with the template metaprogramming solution, the program has still do the conversion of numbers to strings at runtime, and those function calls also cost unnecessary time. Couldn't we just compose the complete text at compile time, and just output it at run time? Well, with the preprocessor, that's indeed possible: |
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< |
<cpp>#include <iostream> |
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#include <ostream> |
#include <ostream> |
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{ |
{ |
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std::cout << SONG; |
std::cout << SONG; |
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}</ |
}</cpp> |
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An inspection of the generated executable proves that it indeed contains the complete text of the song in one block. |
An inspection of the generated executable proves that it indeed contains the complete text of the song in one block. |
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