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+title:C C11 standart _Generic keyword
+keywords:c,c11,generic
+
+
+# C C11 standart _Generic keyword
+
+## INTRO
+
+
+In C standart c11 is supported new keyword _Generic. It add way how
+we can add at macro level decisitions about variable types. And now is
+possible make some C++ like function "overloading". Here is some variants how
+to use this generic "_Generic". Now could print variables dont looking
+on its type _Generic will deal with it.
+
+
+## EXAMPLES
+
+Detect type
+
+```c
+#define type_str(T) _Generic( (T), int: "int",\
+long: "long",\
+default: "Unknown type")
+```
+
+Now we have define check for 2 types int and long. If there is some type
+undefined then choose default type and print "Unknown type". This is auto
+printf example where you can detect type and print its name. But as in page [1]
+you can add number values and compare types in simple way.
+
+```c
+printf("Type1 %s\n", type_str('a'));
+printf("Type2 %s\n", type_str(1));
+printf("Type3 %s\n", type_str(1l));
+printf("Type4 %s\n", type_str(0.0f));
+```
+
+Also is possible to use generic for 2 or more types but then amount
+of declaration grows. But it means that now according to params
+we can choose best function.
+
+```c
+#define type_str2(T1,T2) _Generic( (T1),\
+int: _Generic((T2),int:"int int", default: "int UNK"),\
+default: "UNK UNK" )
+ 
+printf("Double Type 1 %s\n", type_str2(1,1));
+printf("Double Type 2 %s\n", type_str2(1,0.0f));
+printf("Double Type 3 %s\n", type_str2(.0f,.0f));
+```
+
+Check if types is compatible
+
+
+Strange but some types could be invalid if there is const used, like
+'int' and 'const int'.
+
+```c
+#define is_compatible(x,T) _Generic((x), T:"compatible",\
+default: "non-compatible")
+```
+
+Here is defined 2 types and only (int and int) and (const int and const int)
+is compatible.
+
+```c
+int i1;
+const int i2;
+printf("int       == int,       %s\n", is_compatible(i1,int));
+printf("const int == const int, %s\n", is_compatible(i2,const int));
+printf("int       == const int, %s\n", is_compatible(i1,const int));
+printf("const int == int,       %s\n", is_compatible(i2,int));
+```
+
+
+
+## TESTED
+
+gcc-4.9.1  
+clang-3.4
+
+
+## FILES
+
+ex1.c - one argument generic  
+ex2.c - two argument generic  
+ex3.c - check for compatibility
+
+
+## Links
+http://www.robertgamble.net/2012/01/c11-generic-selections.html  
+http://en.wikipedia.org/wiki/C11_%28C_standard_revision%29  
+https://gcc.gnu.org/wiki/C11Status  
+
+## Downloads
+ex3.c -
+1KiB - http://archive.main.lv/files/writeup/c_c11_standart__generic_keyword/ex3.c  
+ex1.c -
+1KiB - http://archive.main.lv/files/writeup/c_c11_standart__generic_keyword/ex1.c  
+ex2.c - 
+1KiB - http://archive.main.lv/files/writeup/c_c11_standart__generic_keyword/ex2.c  
+source.tar.gz -
+1KiB - http://archive.main.lv/files/writeup/c_c11_standart__generic_keyword/source.tar.gz  
+\ No newline at end of file