C++ String Concatenation operator<<

Question

I have realised my mistake. I was trying to concatenate two strings.

I have just started to learn C++. I have a problem about string concatenation. I don't have problem when I use:

cout << "Your name is"<<name;

But when I try to do it with a string:

string nametext;
nametext = "Your name is" << name;
cout << nametext;

I got an error. How can I concatenate two strings?

`<<` is the "put to" operator for `cout`. It is not used for `std::string` or C style strings (`char *`). — crashmstr, Feb 03 '14 at 13:21
For the future, it's possible to do this with things that just + doesn't work on with `std::ostringstream`. — chris, Feb 03 '14 at 13:22
check out this http://stackoverflow.com/questions/4304662/c-concatenating-strings — Nadeem Shaikh, Feb 03 '14 at 13:23

score 35 · Answer 1 · edited Sep 26 '19 at 12:50

35

For string concatenation in C++, you should use the + operator.

nametext = "Your name is" + name;

edited Sep 26 '19 at 12:50

Kevin

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answered Feb 03 '14 at 13:19

Creris

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Doesn't work, I am getting "Invalid operands to binary expression ('const char *' and 'const char *')" The error lies in this line: std::string helloWorld = "Hello," + " World!"; What am I doing wrong? both "Hello," and " World!" are valid strings (I can declare, assign, and print them seperately), but it's raising some weird error abour char* ? – Gregory Fenn Jan 17 '19 at 15:11
4

@GregoryFenn C++ is trying to be backwards compatible with C therefore a raw literal string, which is `"string"` will be a const char* and not a C++ string. In c++ you cant overload operators that take primitive types on both sides, which means you have to convert one of them to string. This will work: `std::string helloWorld = "Hello" + std::string(" World!");` – Creris Jan 19 '19 at 00:31
Awesome! That makes it a lot clearer :) I'm used to C# so some of these technical points seem quite odd to me, it seems strange to me to try to be backwards compatible, but that's just me. – Gregory Fenn Jan 20 '19 at 10:08
@GregoryFenn Yea the raw literal strings in C++ are very confusing if you dont know about them beforehand – Creris Jan 20 '19 at 18:35

Vlad from Moscow · Answer 2 · 2020-06-16T19:23:11.307

First of all it is unclear what type name has. If it has the type std::string then instead of

string nametext;
nametext = "Your name is" << name;

you should write

std::string nametext = "Your name is " + name;

where operator + serves to concatenate strings.

If name is a character array then you may not use operator + for two character arrays (the string literal is also a character array), because character arrays in expressions are implicitly converted to pointers by the compiler. In this case you could write

std::string nametext( "Your name is " );
nametext.append( name );

or

std::string nametext( "Your name is " );
nametext += name;

score 4 · Answer 3 · edited Nov 21 '19 at 01:00

4

nametext is an std::string but these do not have the stream insertion operator (<<) like output streams do.

To concatenate strings you can use the append member function (or its equivalent, +=, which works in the exact same way) or the + operator, which creates a new string as a result of concatenating the previous two.

edited Nov 21 '19 at 01:00

Kotauskas

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answered Feb 03 '14 at 13:20

eerorika

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score 4 · Answer 4 · answered May 16 '19 at 21:42

You can combine strings using stream string like that:

#include <iostream>
#include <sstream>
using namespace std;
int main()
{
    string name = "Bill";
    stringstream ss;
    ss << "Your name is: " << name;
    string info = ss.str();
    cout << info << endl;
    return 0;
}

score 0 · Answer 5 · answered Feb 03 '14 at 13:21

0

nametext = "Your name is" + name;

I think this should do

answered Feb 03 '14 at 13:21

Minhaj Arfin

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C++ String Concatenation operator<<

5 Answers5

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