View Compilation Error

0_0_22727756_3889.cpp: In function 'Mat operator*(Mat, Mat)':
0_0_22727756_3889.cpp:17:32: error: 'memset' was not declared in this scope
  memset(c.mat, 0, sizeof(c.mat));
                                ^
0_0_22727756_3889.cpp: In function 'Mat operator^(Mat, ll)':
0_0_22727756_3889.cpp:29:32: error: 'memset' was not declared in this scope
  memset(c.mat, 0, sizeof(c.mat));
                                ^