View Compilation Error

0_0_33415882_21067.cpp:11:16: error: expected ')' before '+' token
 #define mid (l + r >> 1)
                ^
0_0_33415882_21067.cpp:20:25: note: in expansion of macro 'mid'
 void merge( int l , int mid , int r ){
                         ^
0_0_33415882_21067.cpp:11:16: error: expected ')' before '+' token
 #define mid (l + r >> 1)
                ^
0_0_33415882_21067.cpp:20:25: note: in expansion of macro 'mid'
 void merge( int l , int mid , int r ){
                         ^
0_0_33415882_21067.cpp:11:16: error: expected initializer before '+' token
 #define mid (l + r >> 1)
                ^
0_0_33415882_21067.cpp:20:25: note: in expansion of macro 'mid'
 void merge( int l , int mid , int r ){
                         ^