View Compilation Error

0_0_19050570_25658.cpp: In function 'int main()':
0_0_19050570_25658.cpp:25:16: error: 'r' was not declared in this scope
    while( fabs(r-l) >= 1e-10 ){
                ^
0_0_19050570_25658.cpp:25:18: error: 'l' was not declared in this scope
    while( fabs(r-l) >= 1e-10 ){
                  ^