Essential C++ 第四章小結

隨手畫了一個圖小結一下：

下面是根據書中的例子寫的一些代碼：

#include <iostream>
#include <vector>
#include "Triangulate_iterator.h"
using namespace std;

static int arr[13] = {1,1,2,3,5,8,13,21,34,55,89,144,233};

class Triangulate_iterator;

class Triangulate {
public:

    typedef Triangulate_iterator iterator;
    /*申明Triangulate_iterator爲Triangulate的友元，
    Triangulate_iterator裏的函數都能對Triangulate的私有成員進行訪問了
    */
    friend class Triangulate_iterator;
    Triangulate();
    Triangulate(int length , int beg_pos);
    Triangulate(int length);
    Triangulate(const Triangulate&);

    Triangulate_iterator begin();

    Triangulate_iterator end();

    friend int operator* (const Triangulate_iterator &rhs);

    int length() const { return _length; }
    int beg_pos() const { return _beg_pos; }
    int length() { return _length; }
    int beg_pos() { return _beg_pos; }

    bool next(int &x) const;
    void next_reset() const;

    static bool is_elem( int );
    static int get_elem( int pos ) {
        return _elem[pos];
    }
    static void gen_elements( int length );
    static void gen_elems_to_value( int value );
    static void display( int length, int beg_pos, ostream &os = cout );
    static vector<int> _elem;

private:
    string _name;
    int _length;
    int _beg_pos;
    mutable int _next;

    static const int _max_elems = 1024;


};

class Triangulate_iterator {
public:
    friend class Triangulate;
    Triangulate_iterator(int index) : _index(index-1) {}

    friend int operator* (const Triangulate_iterator &rhs);

    bool operator== ( const Triangulate_iterator& ) const;
    bool operator!= ( const Triangulate_iterator& ) const;

    int Triangulate_iterator::operator* (const Triangulate_iterator &rhs);
    Triangulate_iterator& operator++ ();
    Triangulate_iterator operator++ ( int );

private:
    void check_integrity() const;  //檢查 _index是否合理
    int _index;
};

class iterator_overflow{

};

int operator* (const Triangulate_iterator &rhs) {
    rhs.check_integrity();
    return Triangulate::_elem[rhs._index];
}
inline bool Triangulate_iterator::operator == ( const Triangulate_iterator& rhs ) const {
    return this->_index == rhs._index;
}

inline bool Triangulate_iterator::operator != ( const Triangulate_iterator& rhs ) const {
    return (! (*this == rhs ));
}
inline
int Triangulate_iterator::operator* (const Triangulate_iterator &rhs) {
    rhs.check_integrity();
    return Triangulate::_elem[_index];
}

Triangulate_iterator& Triangulate_iterator::operator++ () {
    _index++;
    check_integrity();
    return *this;
}

Triangulate_iterator Triangulate_iterator::operator++ ( int ) {
    Triangulate_iterator tem = *this;
    _index++;
    check_integrity();
    return tem;
}

inline
void Triangulate_iterator::check_integrity() const {
    if ( _index >= Triangulate::_max_elems)
        throw iterator_overflow();
    if(_index >= Triangulate::_elem.size())
        Triangulate::gen_elements( _index + 1);
}


Triangulate_iterator Triangulate::begin() {
        return Triangulate_iterator(_beg_pos);
    }

Triangulate_iterator Triangulate::end() {
    return Triangulate_iterator(_beg_pos + _length);
}

Triangulate::Triangulate()
    : _name("Triangulate"),_length(1),_beg_pos(1),_next(0) {}
Triangulate::Triangulate(int l, int b) : _name("Triangulate") {
    _length = l > 0 ? l : 1;
    _beg_pos = b > 0 ? b : 1;
    _next = _beg_pos-1;
}

Triangulate::Triangulate(int l) : _name("Triangulate") {
    _length = l > 0 ? l : 1;
    _beg_pos = 1;
    _next = _beg_pos - 1;

}

Triangulate::Triangulate(const Triangulate &rhs) {
    _length = rhs._length;
    _beg_pos = rhs._beg_pos;
    _next = rhs._next;
    _name = rhs._name;
}

bool Triangulate::next(int &elem) const {
    if(_next >= _length)
        return false;
    elem = _elem[_next];
    _next++;
    return true;
}

void Triangulate::next_reset() const {
    _next = _beg_pos - 1;
}

vector<int> Triangulate::_elem;

int sum( const Triangulate &trian ) {
    if ( !trian.length())
        return 0;
    int sum = 0;
    int val = 0;
    trian.next_reset();
    while ( trian.next( val ))
        sum += val;
    return sum;
}

bool Triangulate::is_elem( int value ) {
    if ( !_elem.size() || _elem[_elem.size()-1] < value)
        gen_elems_to_value(value);

    vector<int>::iterator found;
    vector<int>::iterator last = _elem.end();
    found = find(_elem.begin(), last, value);
    return found != last;
}

void Triangulate::gen_elems_to_value( int value ) {
    int ix = _elem.size();
    if ( !ix ) {
        _elem.push_back(1);
        ix = 1;
    }
    if ( ix == 1) {
        _elem.push_back(1);
        ix = 2;
    }
    while ( _elem[ix-1] < value && ix < _max_elems) {
        _elem.push_back(_elem[ix-2] + _elem[ix-1]);
        ix++;
    }

    if( ix == _max_elems )
        cerr << " value too large " << value << " -- exceeds max size of "
            << _max_elems << endl;


}

void Triangulate::gen_elements( int length ) {
    if ( length <= 0 || length > _max_elems )
        return;
    int ix = _elem.size();
    if ( length == 1 && ix < length ) {
        _elem.push_back(1);
        ix++;
    }
    if ( length == 2 && ix < length ) {
        if( ix == 0) {
            _elem.push_back(1);
            ++ix;
        }
        _elem.push_back(1);
        ++ix;
    }

    for (; ix < length; ix++ ) {
        _elem.push_back(_elem[ix-2] + _elem[ix-1]);
    }
}


int main() {
    char ch;
    bool more = true;
    int i = Triangulate::_elem[0];
    while( more ) {
        cout << "Enter your value ";
        int value;
        cin >> value;

        cout << "the value " << (Triangulate::is_elem(value) ? "is " : "is not ")
            << "the element of the Triangulate "
            << " try more (y/n) " << endl;
        cin >> ch;

        if ( ch=='y' || ch=='Y' ) {
            more = true;
        } else
            more = false;

    }
    return 0;

}