This is a gcc extension called case ranges, this is how it is explained in the document: You can specify a range of consecutive values in a single case label, like this: case low … high: You can find a complete list of gcc extensions here. It seems like clang also supports this to try … Read more
It assigns user input value to a and prints it out. it is done by using a Statement Expression. Statement Expressions are a gnu gcc compiler extension and are not supported by the C/C++ standards. Hence, any code which uses statement expression is not standard conforming and non-portable. The IBM XL C/C++ v7.0 also support … Read more
… is an extension provided by GCC https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated-Inits To initialize a range of elements to the same value, write [first … last] = value. This is a GNU extension. For example, int widths[] = { [0 … 9] = 1, [10 … 99] = 2, [100] = 3 }; && is another extension https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels-as-Values You … Read more