answer.cpp:$14$:$16$: error: invalid operands to binary expression $(\text{'}$string$\text{'}($aka 'basic$\_$string'$)$ and 'char'$)$

while $($choice $!=\text{'}$E$\text{'}$ && choice $!=\text{'}$e$\text{'})$; $\}$

~~~~~~ $^$ ~~~