Question

I keep getting this error: postfix.cpp: In function ‘double RPN_evaluation(std::string)’: postfix.cpp:42:26: error: cannot convert ‘__gnu_cxx::__alloc_traits > >::value_type {aka std::basic_string }’ to ‘char’ for argument ‘1’ to ‘int isOperand(char)’ if(isOperand(expr.at(g))){ ^ postfix.cpp:96:1: warning: control reaches end of non-void function [-Wreturn-type] } I am not sure what I am doing wrong, help please

Answer 1

Answer:

expr.at(g) returns a string, not a char. They are not the same thing and that is what the compiler is complaining about.