Guard statement (from Swift) in C++

guardFunction.cpp

#include <iostream>

using namespace std;

// Guard function
template <typename Condition, typename Function>
bool guard(const Condition& condition, Function function) {

	if (bool(!condition)) {
		function();
		return true;
	}
	return false;
}

// Example using the return value
template <typename Type>
Type biggestNumber(Type* numbers, const size_t& size) {
	
	if (guard(numbers != nullptr, [](){ cerr << "[Error: null pointer found] "; })) { return Type{}; }
	
	Type biggest = 0;
	for (size_t i = 0; i < size; ++i) {
		if (numbers[i] > biggest) {
			biggest = numbers[i];
		}
	}
	
	return biggest;
}

int main() {
	
	boolalpha(cout);
	
	int* i = new int{10}; // nullptr;
	
	guard(i != nullptr, [](){ cerr << "Null pointer" << endl; exit(1); });
	guard(*i == 11, [](){ cerr << "Incorrect value" << endl; });
	
	delete i;
	
	//
	double* numbers = nullptr; //new double[4]{1.1, 2.3, 9.01, 9.0};
	cout << "Biggest number: " << biggestNumber(numbers, 4) << endl;
	
	delete[] numbers;
}