模板元编程2.1习题-第二章习题

// 2.1 题目

#include

#include

#include

// 前置声明

template

class replace_compoundtype;

template

class replace_simpletype;

template

class replace_type;

// 基本替换类型，所有无法匹配的默认版本

template

class replace_type_

{

public:

static const bool bSame = boost::is_same::value;

// 选择一下

typedef typename boost::mpl::if_c

V,

T>::type type;

};

// T is a simple type

template

class replace_type_

{

public:

static const bool bConst = boost::is_const::value;

// 选择一下

typedef typename boost::mpl::if_c

typedef typename replace_type_::type,V>::type,

typedef typename boost::add_const::type>::type

>::type type;

};

template

class replace_type_

{

public:

static const bool bVolatile = boost::is_volatile::value;

// 选择一下

typedef typename boost::mpl::if_c

typedef typename replace_type_::type,V>::type,

typedef typename boost::add_volatile::type>::type

>::type type;

};

template

class replace_type_

{

public:

static const bool bVolatile = boost::is_volatile::value;

// 选择一下

typedef typename boost::mpl::if_c

typedef typename replace_type_::type,V>::type,

typedef typename boost::add_volatile<

typedef typename replace_type_::type

>::type 

>::type type;

};

template

class replace_type_

{

public:

static const bool bCompound = boost::is_compound::value;

// 选择一下

typedef typename boost::mpl::if_c

typename replace_compoundtype::type,

typename replace_simpletype::type>::type type_;

typedef typename boost::add_pointer::type type;

};

template

class replace_type_

{

public:

static const bool bCompound = boost::is_compound::value;

// 选择一下

typedef typename boost::mpl::if_c

typename replace_compoundtype::type,

typename replace_simpletype::type >::type type;

};

template

class replace_type_

{

public:

static const bool bCompound = boost::is_compound::value;

// 选择一下

typedef typename boost::mpl::if_c

typename replace_compoundtype::type,

typename replace_simpletype::type >::type type_;

typedef typename boost::add_reference::type type;

};

template

class replace_type_

{

public:

static const bool bCompound = boost::is_compound::value;

// 选择一下

typedef typename boost::mpl::if_c

typename replace_compoundtype::type,

typename replace_simpletype::type >::type type;

};

// T is a simple type

template

class replace_simpletype

{

public:

typedef typename replace_type_::type type;

};

template

class replace_function

{

public:

typedef T type;

};

// 这儿简单些，我支持0 or 1个参数

template

class replace_function

{

public:

typedef typename replace_type::type R_;

typedef typename replace_type::type P1_;

typedef R_ (*PTR)(P1_) ;

typedef PTR type;

};

template

class replace_function

{

public:

typedef typename replace_type_::type R_;

typedef R_ (*PTR)();

typedef PTR type;

};

//

template

class replace_type_

{

public:

typedef typename replace_function::type type;

};

template

class replace_type_

{

public:

typedef typename replace_function::type type;

};

// T  is a compound type

template

class replace_compoundtype

{

public:

// 区分引用 ，数组，指针，函数指针 4种类型; 成员函数指针除外

static const bool bArray = boost::is_array::value;

static const bool bRef = boost::is_reference::value;

static const bool bPointer = boost::is_pointer::value;

static const bool bFuncPointer = boost::is_function::value;

typedef typename boost::mpl::if_c

typename typename replace_function::type,

typename typename replace_type_::type>::type typeFunctionPtrOrDefault;

typedef typename boost::mpl::if_c

typename replace_type_::type,

typeFunctionPtrOrDefault>::type typePtrOrNot;

typedef typename boost::mpl::if_c

typename replace_type_::type,

typePtrOrNot>::type typeRefOrNot;

typedef typename boost::mpl::if_c

typename replace_type_::type ,U,V>::type,

typeRefOrNot>::type typeArrayOrNot;

typedef typename boost::mpl::if_c

typeFunctionPtrOrDefault,

typedef typename boost::mpl::if_c

typeRefOrNot,

typedef typename boost::mpl::if_c

typePtrOrNot,

typedef typename boost::mpl::if_c

typeFunctionPtrOrDefault,

T>::type

>::type

>::type

>::type type;

};

// 这个问题，我理解为处理基本类型，处理数组，处理函数指针,且函数指针携带的类型是基本类型cv

// 其中基本类型也就 is_compound 表示未false_type的那类cv or ;else 就是复合类型

// 另外U V是cv 的基本类型,或者& *

template

class replace_type

{

public:

static const bool bCompound = boost::is_compound::value;

// 选择一下

typedef typename boost::mpl::if_c

typename replace_compoundtype::type,

typename replace_simpletype::type >::type type;

};

int _tmain(int argc, _TCHAR* argv[])

{

// 2.1 练习题

// simple类型测试 

{

// 对ref添加 add_volatile / add_const 那么将保持原类型输出

float f = (float)0.1;

boost::add_volatile::type i = f;

boost::add_const::type i2 = f;

replace_type::type f1 = 0; // float

replace_type::type f2 = 0; // const float

replace_type::type f3 = 0; // volatile float

replace_type::type f4 = 0; // const volatile float

replace_type::type f5 = f; // volatile float& == float&

replace_type::type f6 = 0; // const float

replace_type::type f7 = 0; // const float

}

{

float f = (float)0.1;

volatile float & ff = f;

replace_type::type f1 = 0; // float*

replace_type::type f2 = 0; // const float*

replace_type::type f3 = 0; // volatile float*

replace_type::type f4 = 0; // const volatile float*

replace_type::type f5 = f; // volatile float& = float&

replace_type::type f6 = f;// const float&

replace_type::type f7 = 0; // const float**

f=1.0;

}

{

float f = (float)0.1;

replace_type::type f1 = f; // float&

replace_type::type f2 = 0; // const float&

replace_type::type f3 = f; // volatile float&

replace_type::type f4 = 0; // const volatile float&

replace_type::type f5 = 0; // volatile float*

replace_type::type f6 = 0;//const float*

replace_type::type f7 = f; // const float&

f=1.0;

}

// 函数替换

{

float f = 0.;

replace_type::type f1; // float& (*)()

replace_type::type f2; // float& (*)(float)

replace_type::type f3; // float& (*)(float)

replace_type::type f4; // float& (*)(cv float&)

f = 1.0;

}

return 0;

}

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chinaunix网友2011-03-07 08:46:33

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