CLX C++ Libraries
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Declarations

template <class ConstrainedFunc>
class constrained_value;

Overview

constrained_value は，制約付きの値型を実現するためのクラスです． 代入演算子をオーバーロードすることによって，値の代入や四則演算が行われるたびに， 値が制約を満たしているか自動的にチェックします．制約は ConstrainedFunc に制約条件用のポリシークラスを指定することによってよって与えます． 独自に制約条件用のポリシークラスを定義する場合には，以下の型， およびメソッドを定義する必要があります．

class constrained_func {
public:
  typedef ... value_type;
  
  static void assign(value_type& dest, const value_type& src);
};

尚，現在のところ代入された値が [Min, Max] の範囲外である場合には，std::ranged_error を例外として送出する ranged_integer と言う制約条件用ポリシークラスを提供しています．

template <int Min, int Max>
class ranged_integer {
public:
    typedef int value_type;
    const static value_type default_value = Min;
    
    static void assign(value_type& dest, const value_type& src);
};

代入，四則演算，および比較については，同じ ConstrainedFunc を適用しているオブジェクト， または，基となる型 (integer, double, ...) と行うことができます．

constrained_value は，C++ クックブック (p.194 - 197) をベースに実装しています．

Example

example_constrained_value.cpp

#include <iostream>
#include "clx/constrained_value.h"

int main(int argc, char* argv[])
{
    clx::constrained_value<clx::ranged_integer<0, 100> > x;
    clx::constrained_value<clx::ranged_integer<0, 100> > y;
    clx::constrained_value<clx::ranged_integer<0, 50> > z;
    
    try {
        std::cout << "1st example." << std::endl;
        x = 32;
        std::cout << "x = " << x << std::endl;
        y = 8;
        std::cout << "y = " << y << std::endl;
        y += x + 51 - (2 * 4);
        std::cout << "y = " << y << std::endl;
    }
    catch (std::range_error& e) {
        std::cerr << "exception: " << e.what() << std::endl;
    }
    
    std::cout << std::endl;
    
    try {
        std::cout << "2nd example." << std::endl;
        x = 32;
        std::cout << "x = " << x << std::endl;
        z = 8;
        std::cout << "z = " << z << std::endl;
        z += z.value() + 51 - (2 * 4);
        std::cout << "z = " << z << std::endl;
    }
    catch (std::range_error& e) {
        std::cerr << "exception: " << e.what() << std::endl;
    }
    
    return 0;
}

Result
1st example.
x = 32
y = 8
y = 83

2nd example.
x = 32
z = 8
exception: out of valied range

Template Parameters

ConstrainedFunc
制約条件を記述したポリシークラスを指定します．

Related Types

typedef ConstrainedFunc func;
typedef typename ConstrainedFunc::value_type value_type;

Construction and Member Functions

constrained_value();
constrained_value(const constrained_value& x);
explicit constrained_value(const value_type& x);
virtual ~constrained_value();

const value_type& value() const;

Operators

constrained_value& operator=(const constrained_value& x);
constrained_value& operator+=(const constrained_value& x);
constrained_value& operator-=(const constrained_value& x);
constrained_value& operator*=(const constrained_value& x);
constrained_value& operator/=(const constrained_value& x);
constrained_value& operator%=(const constrained_value& x);
constrained_value& operator=(const value_type& x);
constrained_value& operator+=(const value_type& x);
constrained_value& operator-=(const value_type& x);
constrained_value& operator*=(const value_type& x);
constrained_value& operator/=(const value_type& x);
constrained_value& operator%=(const value_type& x);
constrained_value& operator>>=(int x);
constrained_value& operator<<=(int x);

Unary Operators

constrained_value operator-();
constrained_value operator+();
constrained_value operator!();
constrained_value operator~();

Binary Operators

friend constrained_value operator+(constrained_value x, const constrained_value& y);
friend constrained_value operator-(constrained_value x, const constrained_value& y);
friend constrained_value operator*(constrained_value x, const constrained_value& y);
friend constrained_value operator/(constrained_value x, const constrained_value& y);
friend constrained_value operator%(constrained_value x, const constrained_value& y);

friend constrained_value operator+(constrained_value x, const value_type& y);
friend constrained_value operator-(constrained_value x, const value_type& y);
friend constrained_value operator*(constrained_value x, const value_type& y);
friend constrained_value operator/(constrained_value x, const value_type& y);
friend constrained_value operator%(constrained_value x, const value_type& y);
friend constrained_value operator+(const value_type& y, constrained_value x);
friend constrained_value operator-(const value_type& y, constrained_value x);
friend constrained_value operator*(const value_type& y, constrained_value x);
friend constrained_value operator/(const value_type& y, constrained_value x);
friend constrained_value operator%(const value_type& y, constrained_value x);

friend constrained_value operator>>(constrained_value x, int y);
friend constrained_value operator<<(constrained_value x, int y);

Stream Operators

template <class Ch, class Tr>
friend std::basic_ostream<Ch, Tr>& operator<<(
  std::basic_ostream<Ch, Tr>& sout, constrained_value x);

template <class Ch, class Tr>
friend std::basic_istream<Ch, Tr>& operator>>(
  std::basic_istream<Ch, Tr>& sin, constrained_value x);

Comparison Operators

friend bool operator<(const constrained_value& x, const constrained_value& y);
friend bool operator>(const constrained_value& x, const constrained_value& y);
friend bool operator<=(const constrained_value& x, const constrained_value& y);
friend bool operator>=(const constrained_value& x, const constrained_value& y);
friend bool operator==(const constrained_value& x, const constrained_value& y);
friend bool operator!=(const constrained_value& x, const constrained_value& y);

friend bool operator<(const constrained_value& x, const value_type& y);
friend bool operator>(const constrained_value& x, const value_type& y);
friend bool operator<=(const constrained_value& x, const value_type& y);
friend bool operator>=(const constrained_value& x, const value_type& y);
friend bool operator==(const constrained_value& x, const value_type& y);
friend bool operator!=(const constrained_value& x, const value_type& y);
friend bool operator<(const value_type& y, const constrained_value& x);
friend bool operator>(const value_type& y, const constrained_value& x);
friend bool operator<=(const value_type& y, const constrained_value& x);
friend bool operator>=(const value_type& y, const constrained_value& x);
friend bool operator==(const value_type& y, const constrained_value& x);
friend bool operator!=(const value_type& y, const constrained_value& x);

References

  1. D. Ryan Stephens, Christopher Diggins, Janathan Turkanis, and Jeff Cogswell (株式会社クイープ訳), "C++ クックブック," 株式会社オライリー・ジャパン, 2006.
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