How to Fix “no match for ‘operator<<’” in C++

Short answer: you tried to print something C++ doesn’t know how to print. std::cout << works for built-in types such as int and double, and for library types such as std::string, but not for a std::vector, your own struct or class, or an enum class. Print the parts one at a time, or write an operator<< for your type.

How to Read the Error

The message names the types on both sides of the <<:

error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'Point')

The first type, std::ostream, is std::cout. The second type is the thing C++ can’t print, here a Point. It tells you which of the causes below you’re looking at.

Under the error, GCC and Clang list a long run of “candidates”: every operator<< they tried, for int, char, const char* and so on. You can skip that list. None of them fit, which is exactly what the error is saying.

Cause 1: Printing a Vector

#include <iostream>
#include <vector>

int main() {
    std::vector<int> scores = {90, 85, 77};
    std::cout << scores << '\n';
}

GCC:    error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'std::vector<int>')
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'std::vector<int>')
MSVC:   error C2679: binary '<<': no operator found which takes a right-hand operand of type 'std::vector<int,std::allocator<int>>' (or there is no acceptable conversion)

The standard library doesn’t give std::vector an operator<<, so you print the elements yourself.

Fix: loop over the vector and print each element:

#include <iostream>
#include <vector>

int main() {
    std::vector<int> scores = {90, 85, 77};
    for (int s : scores) {
        std::cout << s << ' ';
    }
    std::cout << '\n';
}

90 85 77

With C++23, std::println from <print> can print a whole vector: std::println("{}", scores); prints [90, 85, 77]. It needs a recent compiler. In our tests it worked with GCC 15, Clang 21 and the latest MSVC with /std:c++latest, but GCC 14 rejected it. For more options, see how to print a vector.

Cause 2: Printing Your Own Struct or Class

#include <iostream>

struct Point {
    int x;
    int y;
};

int main() {
    Point p{3, 4};
    std::cout << p << '\n';
}

GCC:    error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'Point')
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'Point')
MSVC:   error C2679: binary '<<': no operator found which takes a right-hand operand of type 'Point' (or there is no acceptable conversion)

C++ can’t guess how a Point should look on screen. You tell it by writing an operator<<:

#include <iostream>

struct Point {
    int x;
    int y;
};

std::ostream& operator<<(std::ostream& out, const Point& p) {
    return out << '(' << p.x << ", " << p.y << ')';
}

int main() {
    Point p{3, 4};
    std::cout << p << '\n';
}

(3, 4)

Three details matter:

1. It takes the stream first and your object second.
2. It takes your object by const reference.
3. It returns the stream, so you can keep chaining, as in std::cout << p << '\n'.

Causes 3 and 4 are what happens when the first two go wrong. For the full picture, see operator overloading.

Cause 3: operator<< Written as a Member Function

Inside a class, it feels natural to write operator<< as a member function. It compiles, but std::cout << p still fails:

#include <iostream>

class Point {
public:
    Point(int x, int y) : x(x), y(y) {}
    std::ostream& operator<<(std::ostream& out) const {
        return out << '(' << x << ", " << y << ')';
    }
private:
    int x, y;
};

int main() {
    Point p(3, 4);
    std::cout << p << '\n';
}

GCC:    error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'Point')
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'Point')
MSVC:   error C2679: binary '<<': no operator found which takes a right-hand operand of type 'Point' (or there is no acceptable conversion)

A member operator always has its own object on the left. This one handles p << std::cout, which really does compile and print (3, 4), but nobody wants to write that. For std::cout << p, the stream must be on the left, so the operator can’t be a member of Point.

Fix: make it a friend. It’s written inside the class and can read the private members, but it isn’t a member function:

#include <iostream>

class Point {
public:
    Point(int x, int y) : x(x), y(y) {}
    friend std::ostream& operator<<(std::ostream& out, const Point& p) {
        return out << '(' << p.x << ", " << p.y << ')';
    }
private:
    int x, y;
};

int main() {
    Point p(3, 4);
    std::cout << p << '\n';
}

(3, 4)

See friend functions for how friend works.

Cause 4: operator<< Without const

This version takes Point& instead of const Point&:

#include <iostream>

struct Point {
    int x;
    int y;
};

std::ostream& operator<<(std::ostream& out, Point& p) {
    return out << '(' << p.x << ", " << p.y << ')';
}

int main() {
    const Point origin{0, 0};
    std::cout << origin << '\n';
}

GCC:    error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'const Point')
        error: binding reference of type 'Point&' to 'const Point' discards qualifiers
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'const Point')
        note: candidate function not viable: 2nd argument ('const Point') would lose const qualifier
MSVC:   error C2679: binary '<<': no operator found which takes a right-hand operand of type 'const Point' (or there is no acceptable conversion)

A plain Point& can’t refer to a const Point, because nothing would stop the function changing it. Printing a temporary fails for a similar reason: std::cout << Point{1, 2} gives GCC’s cannot bind non-const lvalue reference of type 'Point&' to an rvalue of type 'Point'.

Fix: take the object by const reference, as in Cause 2: const Point& p. Printing shouldn’t change anything, so const is the right promise. See const in C++.

Cause 5: Printing an enum class

#include <iostream>

enum class Color { Red, Green, Blue };

int main() {
    Color c = Color::Green;
    std::cout << c << '\n';
}

GCC:    error: no match for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'Color')
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'Color')
MSVC:   error C2679: binary '<<': no operator found which takes a right-hand operand of type 'Color' (or there is no acceptable conversion)

A plain enum converts to int automatically, so it prints as a number. An enum class deliberately doesn’t convert on its own.

Fix: convert it yourself:

#include <iostream>

enum class Color { Red, Green, Blue };

int main() {
    Color c = Color::Green;
    std::cout << static_cast<int>(c) << '\n';
}

1

To print the name (“Green”) instead of the number, see how to convert an enum to a string. The difference between the two kinds of enum is in enum vs enum class.

Cause 6: The Arrows Point the Wrong Way

<< goes with std::cout and >> goes with std::cin. Swap them and every line gives its own “no match”:

#include <iostream>

int main() {
    int age;
    std::cout >> "Enter your age: ";
    std::cin << age;
}

GCC:    error: no match for 'operator>>' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'const char [17]')
        error: no match for 'operator<<' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'int')
Clang:  error: invalid operands to binary expression ('ostream' (aka 'basic_ostream<char>') and 'const char[17]')
        error: invalid operands to binary expression ('istream' (aka 'basic_istream<char>') and 'int')
MSVC:   error C2676: binary '>>': 'std::ostream' does not define this operator or a conversion to a type acceptable to the predefined operator
        error C2678: binary '<<': no operator found which takes a left-hand operand of type 'std::istream' (or there is no acceptable conversion)

Look at the first type in each message: std::ostream is cout and std::istream is cin. The arrows show which way the data flows. std::cout << x sends x out to the screen, and std::cin >> x sends what you type into x.

Fix: std::cout << "Enter your age: "; and std::cin >> age;. More in getting user input with cin.

Quick Reference

For other common messages, see C++ error messages explained.

Take Your C++ Further

Object-oriented C++ clicks once you have a clear picture of what an object is and how classes relate to each other. C++ Better Explained covers classes, inheritance and polymorphism in plain English, with analogies and code diagrams.

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Related Articles

• C++ Error Messages Explained — the most common errors and what they mean.
• Operator Overloading in C++ — writing operators for your own types.
• Friend Functions in C++ — why operator<< is usually a friend.
• How to Print a Vector in C++ — loops, iterators and more.
• How to Fix ‘no matching function for call to’ — the same kind of error for function calls.