View Compilation Error

0_0_2754296_10559.cpp: In function `bool Evaluate(int, int, int&)':
0_0_2754296_10559.cpp:27: error: `stack' undeclared (first use this function)
0_0_2754296_10559.cpp:27: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_2754296_10559.cpp:27: error: expected primary-expression before "int"
0_0_2754296_10559.cpp:27: error: expected `;' before "int"
0_0_2754296_10559.cpp:28: error: expected primary-expression before "char"
0_0_2754296_10559.cpp:28: error: expected `;' before "char"
0_0_2754296_10559.cpp:44: error: `s1' undeclared (first use this function)
0_0_2754296_10559.cpp:51: error: `s2' undeclared (first use this function)