166 lines
4.2 KiB
Markdown
166 lines
4.2 KiB
Markdown
# DR QUINE
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## 2. GRACE
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#### 2.1 constructing a quine with macro :
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---
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**a quine could be this structure basically :**
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```
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int main()
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{
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char *quine = THE_WHOLE_PROGRAM;
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printf(quine);
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return 0;
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}
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```
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**in one line :**
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```
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int main(){ char *quine = THIS_LINE_&_THE_LINES_AROUND; printf(quine); return 0; }
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```
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**whole code idea :**
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```
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#include <stdio.h>
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#define MAIN() int main() { char *quine = "BEFORE" "THIS_MACRO_ITSELF" "AFTER"; printf(quine); return 0; }
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MAIN()
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```
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#### 2.2 let's try it
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---
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```
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#include <stdio.h>
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#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s"\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }
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MAIN(s)
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```
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**expansions :**
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-> `int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))\n"; printf(quine); return 0; }`
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**exploded view :**
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```
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int main()
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{
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char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))";
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printf(quine);
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return 0;
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}
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```
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**problem :** the `char *quine` string should contain a copy of the whole code in place of "s"
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#### 2.3 second try, macro calling itself : MAIN(MAIN)
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---
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```
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#include <stdio.h>
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#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s"\n\nMAIN(MAIN(s))\n"; printf(quine); return 0; }
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MAIN(MAIN(s))
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```
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**expansions :**
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-> `int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))"; printf(quine); return 0; }"\n\nMAIN(MAIN(s))\n"; printf(quine); return 0; }`
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**exploded view :**
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```
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int main()
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{
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char *quine = "#include <stdio.h>\n#define MAIN(s) "int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))"; printf(quine); return 0; }"\n\nMAIN(MAIN(s))\n";
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printf(quine);
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return 0;
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}
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```
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**problem :** almost there, but the content of the string quine should be a litteral string instead of code
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#### 2.4 lets stringify the content of the inner MAIN
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---
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**the previous can be written with an extra step :**
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```
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#define str(s) s
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#define MAIN(s) content s content
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MAIN(str(MAIN(s)))
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/* EQUIVALENT */
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#define MAIN(s) content s content
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MAIN((MAIN(s)))
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```
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**we can use this extra step to stringify the content :**
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```
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#include <stdio.h>
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#define str(s) #s
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#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define str(s) #s\n#define MAIN(s) "s"\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }
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MAIN(str(MAIN(s)))
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```
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**expansions :**
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-> `int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) ""MAIN(s)""\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }`
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**exploded view :**
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```
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int main()
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{
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char *quine = "#include <stdio.h>\n#define MAIN(s) ""MAIN(s)""\n\nMAIN(str(MAIN(s)))";
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printf(quine);
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return 0;
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}
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```
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**problem :** oops, it stringified the parameter name, not it's expanded version, see https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html
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#### 2.5 working stringification
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---
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```
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#include <stdio.h>
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#define xstr(s) #s
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#define str(s) xstr(s)
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#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define xstr(s) #s\n#define str(s) xstr(s)\n#define MAIN(s) "s"\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }
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MAIN(str(MAIN(s)))
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```
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**expansions :**
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-> `int main() { char *quine = "#include <stdio.h>\n#define xstr(s) #s\n#define str(s) xstr(s)\n#define MAIN(s) ""int main() { char *quine = \"#include <stdio.h>\\n#define xstr(s) #s\\n#define str(s) xstr(s)\\n#define MAIN(s) \"s\"\\n\\nMAIN(str(MAIN(s)))\\n\"; printf(quine); return 0; }""\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }`
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**exploded view :**
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```
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int main()
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{
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char *quine =
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"#include <stdio.h>\n#define xstr(s) #s\n#define str(s) xstr(s)\n#define MAIN(s) "
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"int main() { char *quine = \"#include <stdio.h>\\n#define xstr(s) #s\\n#define str(s) xstr(s)\\n#define MAIN(s) \"s\"\\n\\nMAIN(str(MAIN(s)))\\n\"; printf(quine); return 0; }"
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"\n\nMAIN(str(MAIN(s)))\n";
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printf(quine);
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return 0;
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}
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```
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**output :**
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```
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#include <stdio.h>
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#define xstr(s) #s
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#define str(s) xstr(s)
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#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define xstr(s) #s\n#define str(s) xstr(s)\n#define MAIN(s) "s"\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }
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MAIN(str(MAIN(s)))
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```
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**victory ;)**
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