step by step explanation of grace

README.md

@@ -1 +1,163 @@
-# DR_QUINE
+# DR QUINE
+
+#### constructing a quine with macro :
+---
+
+**a quine could be this structure basically :**
+```
+int main()
+{
+	char *quine = THE_WHOLE_PROGRAM;
+	printf(quine);
+	return 0;
+}
+```
+
+**in one line :**
+```
+int main(){ char *quine = THIS_LINE_&_THE_LINES_AROUND; printf(quine); return 0; }
+```
+
+**whole code idea :**
+```
+#include <stdio.h>
+#define MAIN() int main() { char *quine = "BEFORE" "THIS_MACRO_ITSELF" "AFTER"; printf(quine); return 0; }
+
+MAIN()
+```
+
+
+#### let's try it
+---
+
+```
+#include <stdio.h>
+#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; }
+
+MAIN(s)
+```
+
+**expansions :**
+-> `int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))\n"; printf(quine); return 0; }`
+
+**exploded view :**
+```
+int main()
+{
+	char *quine = "#include <stdio.h>\n#define MAIN(s) "s "\n\nMAIN(MAIN(s))";
+	printf(quine);
+	return 0;
+}
+```
+
+**problem :** the `char *quine` string should contain a copy of the whole code in place of "s"
+
+
+#### second try
+---
+
+```
+#include <stdio.h>
+#define MAIN(s) int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) "s"\n\nMAIN(MAIN(s))\n"; printf(quine); return 0; }
+
+MAIN(MAIN(s))
+```
+
+**expansions :**
+-> `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; }`
+
+**exploded view :**
+```
+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;
+}
+```
+
+**problem :** almost there, but the content of the string quine should be a litteral string instead of code
+
+
+
+#### lets stringify the content of the string quine
+---
+
+**the previous can be written with an extra step :**
+```
+#define str(s) s
+#define MAIN(s) content s content
+MAIN(str(MAIN(s)))
+
+/* EQUIVALENT */
+
+#define MAIN(s) content s content
+MAIN((MAIN(s)))
+```
+
+**we can use this extra step to stringify the content :**
+```
+#include <stdio.h>
+#define str(s) #s
+#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; }
+
+MAIN(str(MAIN(s)))
+```
+
+**expansions :**
+-> `int main() { char *quine = "#include <stdio.h>\n#define MAIN(s) ""MAIN(s)""\n\nMAIN(str(MAIN(s)))\n"; printf(quine); return 0; }`
+
+
+**exploded view :**
+```
+int main()
+{
+	char *quine = "#include <stdio.h>\n#define MAIN(s) ""MAIN(s)""\n\nMAIN(str(MAIN(s)))";
+	printf(quine);
+	return 0;
+}
+```
+
+**problem :** oops, it stringified the paramter name, not it's expanded version, see https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html
+
+
+#### working stringification
+---
+
+```
+#include <stdio.h>
+#define xstr(s) #s
+#define str(s) xstr(s)
+#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; }
+
+MAIN(str(MAIN(s)))
+```
+
+**expansions :**
+-> `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; }`
+
+**exploded view :**
+```
+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;
+}
+```
+
+**output :**
+```
+#include <stdio.h>
+#define xstr(s) #s
+#define str(s) xstr(s)
+#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; }
+
+MAIN(str(MAIN(s)))
+```
+
+**victory ;)**
+