CODEWITHSUNDEEP
c++stringpointers
user379888
user379888

Reputation:

C++, Invalid conversion from ‘char’ to ‘const char*’

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?

Upvotes: 9

Views: 31973

Answers (4)

Nicol Bolas
Nicol Bolas

Reputation: 474476

There is no std::string::insert that takes only a position and a character. What you want is insert(0, 1, '('), which inserts 1 character at position 0.

The same goes for std::string::append: append(1, ')')

Upvotes: 5

Marlon
Marlon

Reputation: 20332

Now I don't get why does the compiler says I am converting from char to const char*.

The reason you are getting a compilation error is because there is no matching overload for the set of arguments you are passing to the method. The compiler tries to find the closest match, which in your case char and const char*, and then reports that error.

Please help me out.

There are 8 overloads for std::string::insert and 6 overloads for std::string::append. You have many different options such as:

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

or

expression_input.insert(expression_input.begin(), '(');
expression_input.append(")");

or even

expression_input.insert(0, 1, '(');
expression_input.append(")");

There's many possibilities, just choose one that you find most readable or sutiable for your situation.

Upvotes: 3

minus
minus

Reputation: 706

the version of string::insert function you are using requires const char* you are putting in char use " instead of '

here is a link to method documentation

http://www.cplusplus.com/reference/string/string/insert/

Upvotes: 0

Paul R
Paul R

Reputation: 213210

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(")");

Upvotes: 11

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