How do I concatenate strings with chars in C++?

Question

I've got a function which takes a string, let's call it

void print(std::string myString) 
{ 
    std::cout << myString;
}

I want to do something like

char myChar;
myChar = '{';
print("Error, unexpected char: " + myChar + "\n");

It doesn't work.

I tried something like

print(std::string("Error, unexpected char") + std::string(myChar) + std::string("\n) )

but then std::string(myChar) becomes whatever int the char represents, it's printed as an int and isn't printed as it's alphanumeric representation!

There is no constructor of std::string which converts a char into its digits. Did you perhaps use std::to_string? — Robert Andrzejuk
– Robert Andrzejuk, Commented Apr 18, 2020 at 12:38
@RobertAndrzejuk i did, but i wanted the newline in there instead of putting it in my print function. Also, yeah I used tostring forgot sorry — Shazamo Morebucks
– Shazamo Morebucks, Commented Apr 18, 2020 at 12:40
If ... +ch+"\n" doesn't work, then the newline can be written as: "\n"s — Robert Andrzejuk
– Robert Andrzejuk, Commented Apr 18, 2020 at 12:45
@ShazamoMorebucks it's printed as an int and isn't printed as it's alphanumeric representation! -- I'm surprised no one so far has actually explained the issue. You used the wrong std::string constructor. It should have been std::string(1, myChar); — PaulMcKenzie
– PaulMcKenzie, Commented Apr 18, 2020 at 13:15

halfer · Accepted Answer · 2021-09-26 10:32:22Z

2

The function should be declared like:

void print( const std::string &myString) 
{ 
    std::cout << myString;
}

and called like:

print( std::string( "Error, unexpected char: " ) + myChar + "\n");

As for your comment:

as a follow up, would it have been possible to pass an anonymous function returning a string as an argument to print()? Something like print( {return "hello world";}

then you can do this as it is shown in the demonstration program:

#include <iostream>
#include <string>

void f( std::string h() )
{
    std::cout << h() << '\n';
}

int main() 
{
    f( []()->std::string { return "Hello World!"; } );
    
    return 0;
}

edited Sep 26, 2021 at 10:32

halfer

20.2k20 gold badges110 silver badges207 bronze badges

answered Apr 18, 2020 at 12:34

Vlad from Moscow

313k27 gold badges204 silver badges358 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Shazamo Morebucks Over a year ago

It works! Looks like what I did wrong was passing print(std::string("Unexpected Character " + character) + '\n') as the argument, i should have kept the literal and character separate

Shazamo Morebucks Over a year ago

as a follow up, would it have been possible to pass an anonymous function returning a string as an argument to print()? Something like print( [](){return "hello world";})

Vlad from Moscow Over a year ago

@ShazamoMorebucks Here you are #include <iostream> #include <string> void f( std::string h() ) { std::cout << h() << '\n'; } int main() { f( []()->std::string { return "Hello World!"; } ); return 0; }

Shazamo Morebucks Over a year ago

Thanks! So I have to declare an overload to accept a lambda each time? Is there a way to automatically accept lambdas for any argument by default?

Vlad from Moscow Over a year ago

@ShazamoMorebucks If types of lambda expressions converted to functions are different then you have to declare a template function.

con ko · Accepted Answer · 2020-04-18 12:55:15Z

2

If you are using C++14, you can do this:

using namespace std::literals;
char myChar;
myChar = '{';
print("Error, unexpected char: "s + myChar + "\n"s);

answered Apr 18, 2020 at 12:55

con ko

1,5088 silver badges21 bronze badges

1 Comment

Shazamo Morebucks Over a year ago

Thanks! I'm new to c++ so didn't know you could make string literals, thought u always had char array literals

Eklavya · Accepted Answer · 2020-04-18 12:51:10Z

1

You can convert any one and concat.

You can use str.c_str() to convert C++ string to C character array.

Or

Use std::string inbuilt constructor to convert C character array to C++ string.

answered Apr 18, 2020 at 12:51

Eklavya

18.6k4 gold badges33 silver badges62 bronze badges

Collectives™ on Stack Overflow

How do I concatenate strings with chars in C++?

3 Answers 3

5 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related