CODEWITHSUNDEEP
c++stringmultidimensional-array
Aerophite
Aerophite

Reputation: 215

2D string Array C++: Integer Concatenation Into String

I want to start off by saying that I have almost no experience with C++ but I am taking a college class for it this semester and was just sort of messing around so that I am a little better prepared for the class. I know a good amount of Java but almost no C++.

Basically, I want to make some integers part of a string that will go into a string 2D Array. Then I want to print out just to make sure that everything is in the array...I realize that the second for loop isn't really necessary but I put it there anyway.

My problem is that I keep getting an error message when trying to do:

myArray[i][j] = "(" << i << "," << j << ")";

Specifically, it tells me:

error: invalid operands of types 'const char*' and 'const char [2]' to binary 
       'operator+'

I don't understand this error nor do I know how to fix it...

Here is what I have.

int height = 5;
int width = 5;
string myArray[height][width];

for (int i = 0; i < height; ++i) {
    for (int j = 0; j < width; ++j) {
        myArray[i][j] = "(" << i << "," << j << ")";
    }
}

for (int i = 0; i < height; ++i) {
    for (int j = 0; j < width; ++j) {
        cout << myArray[i][j] << "  ";
    }
}

I just want to know how to fix the error and then I would also like to know specifically why I am getting said error. Thanks!

Upvotes: 0

Views: 1179

Answers (2)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361812

You can write a stringbuilder utility in such a way that you would be able to use it as:

myArray[i][j] = stringbuilder() << "(" << i << "," << j << ")";

//other examples
std::string s = stringbuilder() << 25  << " is greater than " << 5;

f(stringbuilder() << a << b << c); //f is : void f(std::string const&);

where stringbuilder is defined as:

struct stringbuilder
{
   std::stringstream ss;
   template<typename T>
   stringbuilder & operator << (const T &data)
   {
        ss << data;
        return *this;
   }
   operator std::string() { return ss.str(); }
};

Note that if you're going to use std::stringstream many times in your code, the stringbuilder reduces the verbosity of your code. Otherwise, you can use std::stringstream directly.

Upvotes: 3

Luchian Grigore
Luchian Grigore

Reputation: 258688

You get the error because that's not the way to concatenate strings in C++. But the message is strange, since you appear to be using operator << and not operator +.

Regardless, use a std::stringstream.

std::stringstream ss;
ss << "(" << i << "," << j << ")";
myArray[i][j] = ss.str();

Upvotes: 4

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