Question

In C++ I have this program:

#include <iostream>
using namespace std;
int main(){
    string expression_input;
    cout << "User Input: " << endl;
    getline(cin, expression_input);
    expression_input.insert(0, '(');   //error happens here.
    expression_input.append(')');
}

I am getting the following error:

prog.cpp:15: error: invalid conversion from ‘char’ to ‘const char*’

prog.cpp:15: error:   initializing argument 2 of 
‘std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, 
_Traits, _Alloc>::insert(typename _Alloc::rebind<_CharT>::other::size_type, 
const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, 
_Alloc = std::allocator<char>]’

Where am I am converting from char to const char*? Can’t I insert a character at position 0 of a string?

Answer 1

The error message tells you everything you need to know – you’re trying to pass a char parameter where a const char * is required.

You just need to change:

expression_input.insert(0,'(');
expression_input.append(')');

to:

expression_input.insert(0,"(");
expression_input.append(")");