Example of std::none_of

Shapes.cc

#include <iostream>
#include <vector>
#include <algorithm>

using std::cout;
using std::vector;
using std::none_of;

struct Shape {
    Shape() {}
    virtual float area() = 0;
    virtual ~Shape() {}
};

class Rectangle : public Shape {
private:
    float height;
    float width;

public:
    float area() override
    {
        return height * width;
    }

    Rectangle(float h, float w) : height(h), width(w) {}
};

class Circle : public Shape {
private:
    float radius;

public:
    float area() override
    {
        return radius * radius * 3.14; // approx
    }

    Circle(float radius) : radius(radius) {}
};

class Triangle : public Shape {
};

int main(int argc, const char *argv[])
{
    constexpr float radius1{3.f};
    constexpr float radius2{2.5f};
    constexpr float height1{2.f};
    constexpr float height2{3.f};
    constexpr float width1{4.f};
    constexpr float width2{1.5f};
    Circle c1(radius1);
    Circle c2(radius2);
    Rectangle r1(height1, width1);
    Rectangle r2(height1, width2);
    Rectangle r3(height2, width1);
    Rectangle r4(height2, width2);
    vector<Shape*> v{&c1, &c2, &r1, &r2, &r2, &r4};
    auto is_triangle = [](Shape* s) { return dynamic_cast<Triangle*>(s) != nullptr; };
    bool no_triangle = none_of(v.cbegin(),
            v.cend(),
            is_triangle);
    if (no_triangle)
        cout << "No triangle\n";
    return 0;
}