View Compilation Error

0_0_15806046_28506.cpp: In function 'bool ok(char*, char*)':
0_0_15806046_28506.cpp:10:22: error: 'strlen' was not declared in this scope
     int Pn = strlen(P), Tn = strlen(T);
                      ^
0_0_15806046_28506.cpp:11:14: error: 'Tn' was not declared in this scope
     if (Pn > Tn) return false;
              ^
0_0_15806046_28506.cpp:16:24: error: 'Tn' was not declared in this scope
     for (int i=0,j=0;i<Tn;++i){
                        ^