View Compilation Error

0_0_25877796_19434.cpp: In function 'mat operator*(mat, mat)':
0_0_25877796_19434.cpp:17:27: error: 'memset' was not declared in this scope
  memset(&ret,0,sizeof(mat));
                           ^
0_0_25877796_19434.cpp: In function 'mat mpow(mat, int)':
0_0_25877796_19434.cpp:30:27: error: 'memset' was not declared in this scope
  memset(&ret,0,sizeof(mat));
                           ^
0_0_25877796_19434.cpp: In function 'int main()':
0_0_25877796_19434.cpp:83:29: error: 'memset' was not declared in this scope
   memset(&temp,0,sizeof(mat));
                             ^