Added notes about _Generic's

1 files changed, 128 insertions, 0 deletions

diff --git a/md/writeup/c_macro_tricks.md b/md/writeup/c_macro_tricks.md
index 759cf70..4068272 100644
--- a/md/writeup/c_macro_tricks.md
+++ b/md/writeup/c_macro_tricks.md
@@ -250,5 +250,133 @@ void mul ( "there is 3");
 void div ( "there is 1");
 ```
 
+## C11 generics
 
+### Match single argument
 
+Best part of it that it can match also typdefed structures. So now macroses 
+can contain typechecking
+
+```
+#define type_str(T) _Generic( (T), int: "int",\
+long: "long",\
+A: "A",\
+default: "Unknown type")
+```
+
+#### Source
+```c
+typedef struct A
+{
+
+} A;
+
+#define type_str(T) _Generic( (T), int: "int",\
+long: "long",\
+A: "A",\
+default: "Unknown type")
+
+int main()
+{
+  A a;
+  printf("%s\n",type_str((long)1));
+  printf("%s\n",type_str((int)1));
+  printf("%s\n",type_str(a));
+}
+```
+
+#### Result
+
+```
+long
+int
+A
+```
+
+### Match multiple arguments
+
+```
+#define type_str(T1,T2) _Generic( (T1),\
+int:   _Generic((T2),int:"int int",   long: "int long",   float: "int float",   A: "int A",   default: "int UNK"),\
+long:  _Generic((T2),int:"long int",  long: "long long",  float: "long float",  A: "long A",  default: "long UNK"),\
+float: _Generic((T2),int:"float int", long: "float long", float: "float float", A: "float A", default: "float UNK"),\
+A:     _Generic((T2),int:"A int",     long: "A long",     float: "A float",     A: "A A",     default: "A UNK"),\
+default: "UNK UNK" )
+```
+
+#### Source
+```
+typedef struct A
+{
+
+} A;
+
+#define type_str(T1,T2) _Generic( (T1),\
+int:   _Generic((T2),int:"int int",   long: "int long",   float: "int float",   A: "int A",   default: "int UNK"),\
+long:  _Generic((T2),int:"long int",  long: "long long",  float: "long float",  A: "long A",  default: "long UNK"),\
+float: _Generic((T2),int:"float int", long: "float long", float: "float float", A: "float A", default: "float UNK"),\
+A:     _Generic((T2),int:"A int",     long: "A long",     float: "A float",     A: "A A",     default: "A UNK"),\
+default: "UNK UNK" )
+
+int main()
+{
+  A a;
+  printf("%s\n",type_str((long)1,1.f));
+  printf("%s\n",type_str((int)1,1));
+  printf("%s\n",type_str(a,a));
+}
+
+```
+
+#### Result
+
+```
+long float
+int int
+A A
+```
+### Generic printf
+```
+#define FF "%f "
+#define FS "%s "
+#define FD "%d "
+#define N ""
+#define PR2(S,T,T1,T2,...) printf(S,T,T1)
+#define PR1(S,T,T1,...) _Generic((T1),\
+  int:  PR2(S FD,T,T1,__VA_ARGS__,N,N,N),\
+  float:PR2(S FF,T,T1,__VA_ARGS__,N,N,N),\
+  char*:PR2(S FS,T,T1,__VA_ARGS__,N,N,N),\
+  default:"")
+#define static_printf(T1,...) _Generic((T1),\ 
+  int:  PR1(FD,T1,__VA_ARGS__,N,N,N),\
+  float:PR1(FF,T1,__VA_ARGS__,N,N,N),\
+  char*:PR1(FS,T1,__VA_ARGS__,N,N,N),\
+  default:"")
+```
+
+#### Source
+```
+int main()
+{
+  A a;
+  int b = 3, c = 4;
+  static_printf(1, 2.f);
+  printf("\n");
+  static_printf(b,c);
+  printf("\n");
+
+  static_printf("big float",0.01f);
+  printf("\n");
+}
+```
+
+#### Result
+
+```
+1 2.000000 
+3 4 
+big float  0.010000
+```
+
+## Links
+1. [https://baike.baidu.com/item/C11](https://baike.baidu.com/item/C11)