spirolator.h

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#ifndef FRECHET_VIEW_SPIROLATOR_H
#define FRECHET_VIEW_SPIROLATOR_H

namespace frechet { namespace data {

class Spirolator {
private:
    int min;    
    int max;    
    int current;    
    int increment;  
public:
    Spirolator(int amin, int amax)
    : min(amin),max(amax),current((amin+amax-1)/2),increment(0)
    { }
    operator bool() { return current >= min && current < max; }
    operator int()  { return current; }
    Spirolator& operator++() {
        ++increment;
        if (increment&1)
            current += increment;   //  add odd numbers
        else
            current -= increment;   //  subtract even numbers
        return *this;
    }
};

} } // namespace

#endif //FRECHET_VIEW_SPIROLATOR_H