SCIP in C++11 ― 2.1.2節

有向線分と長方形：問題2.2～2.3

listやtupleを使ってた頃は型の構造はまんま型の指定に現れていたが、

shared_ptrをtypedefしたListにしてからは、ぱっと見分からないので、

なるべくtypedefして何を扱っているのかわかりやすくした。

これはSchemeではあまり見ない利点かも。

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const double average(const double x1, const double x2)

{return((x1+x2)/2.0);}

//Point

typedef List Point;

const Point makePoint(const double x, const double y)

{return(cons(x,y));}

const double xPoint(const Point p){return(car(p)->getDouble());}

const double yPoint(const Point p){return(cadr(p)->getDouble());}

void printPoint(const Point p)

{

    cout<<"("<<xPoint(p)<<","<<yPoint(p)<<")";

}

//Segment

typedef List Segment;

const Segment makeSegment

(const Point startPoint, const Point endPoint)

{return(makeList(startPoint,endPoint));}

const Point startSegment(const Segment s){return(car(s));}

const Point endSegment(const Segment s){return(cadr(s));}

const Point midPointSegment(const Segment s)

{

    return(makePoint

           (average(xPoint(startSegment(s)),xPoint(endSegment(s))),

            average(yPoint(startSegment(s)),yPoint(endSegment(s)))));

}

const double segmentLength(const Segment s)

{return(sqrt(pow(xPoint(startSegment(s))-xPoint(endSegment(s)),2)

             +pow(yPoint(startSegment(s))-yPoint(endSegment(s)),2)));}

// Rectangle1: definition with 2 diagonal points

typedef List Rectangle;

const Rectangle makeRectangle

(const Point vertex1, const Point vertex3)

{return(makeList(vertex1,vertex3));}

// Rectangle2: definition with a left-lower point and 2 segment lengths

const Rectangle makeRectangle

(const Point vertex3, const double verticalLength,

 const double horizontalLength)

{return(makeRectangle(makePoint(xPoint(vertex3)+horizontalLength,

                                yPoint(vertex3)+verticalLength),

                      vertex3));

}

const Point vertex1Rectangle(const Rectangle rectangle)

{return(car(rectangle));}

const Point vertex3Rectangle(const Rectangle rectangle)

{return(cadr(rectangle));}

const Point vertex2Rectangle(const Rectangle rectangle)

{return(makePoint(xPoint(vertex1Rectangle(rectangle))

                  ,yPoint(vertex3Rectangle(rectangle))));}

const Point vertex4Rectangle(const Rectangle rectangle)

{return(makePoint(xPoint(vertex3Rectangle(rectangle)),

                  yPoint(vertex1Rectangle(rectangle))));}

const Segment verticalSide(const Rectangle rectangle)

{

    const Point vertex1(vertex1Rectangle(rectangle));

    const Point vertex2(vertex2Rectangle(rectangle));

    return(makeSegment(vertex1,vertex2));

}

const Segment horizontalSide(const Rectangle rectangle)

{

    const Point vertex1(vertex1Rectangle(rectangle));

    const Point vertex4(vertex4Rectangle(rectangle));

    return(makeSegment(vertex1,vertex4));

}

const double perimeter(const Rectangle rectangle)

{return(2.0*(segmentLength(verticalSide(rectangle))

             +segmentLength(horizontalSide(rectangle))));

}

const double area(const Rectangle rectangle)

{return((segmentLength(verticalSide(rectangle))

         *segmentLength(horizontalSide(rectangle))));

}

int main(int argc, char** argv)

{

    cout<<"Excersize 2.2:"<<endl;

    const Point A(makePoint(1,2));

    const Point B(makePoint(-1,-1));

   

    cout<<"A";

    printPoint(A);

    cout<<endl;

    cout<<"B";

    printPoint(B);

    cout<<endl;

    const Segment AB(makeSegment(A,B));

    cout<<"the middle point of AB:";

    printPoint(midPointSegment(AB));

    cout<<endl;

    cout<<endl<<"Excersize 2.3:"<<endl

        <<"Rectangle1 (definition with 2 diagonal points):"<<endl;

    const Rectangle rectangle1=makeRectangle(A,B);

    cout<<"perimeter="<<perimeter(rectangle1)<<endl

        <<"area="<<area(rectangle1)<<endl;

    cout<<endl<<

        "Rectangle2 (definition with a left-lower point"<<endl

        <<"and 2 side lengths):"

        <<endl;

    const Rectangle rectangle2=makeRectangle(B,3.0,2.0);

    cout<<"perimeter="<<perimeter(rectangle2)<<endl

        <<"area="<<area(rectangle2)<<endl;

    return(0);

}

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出力

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Excersize 2.2:

A(1,2)

B(-1,-1)

the middle point of AB:(0,0.5)

Excersize 2.3:

Rectangle1 (definition with 2 diagonal points):

perimeter=10

area=6

Rectangle2 (definition with a left-lower point

and 2 side lengths):

perimeter=10

area=6