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"C++Templates The Complete Guide"讀書筆記----Chapter 3

Chapter 3 Class Templates
1. A clas template is a class that is implemented with one or more type parameters left open

#include?<vector>

#include?<stdexcept>

template?<typename?T>

class?Stack?{

??private:

????std::vector<T>?elems;?????//?elements

??public:

????void?push(T?const&);??????//?push?element

????void?pop();???????????????//?pop?element

????T?top()?const;????????????//?return?top?element

????bool?empty()?const?{??????//?return?whether?the?stack?is?empty

????????return?elems.empty();

????}

};

template?<typename?T>

void?Stack<T>::push?(T?const&?elem)

{

????elems.push_back(elem);????//?append?copy?of?passed?elem

}

template<typename?T>

void?Stack<T>::pop?()

{

????if?(elems.empty())?{

????????throw?std::out_of_range("Stack<>::pop():?empty?stack");

????}

????elems.pop_back();?????????//?remove?last?element

}

template?<typename?T>

T?Stack<T>::top?()?const

{

????if?(elems.empty())?{

????????throw?std::out_of_range("Stack<>::top():?empty?stack");

????}

????return?elems.back();??????//?return?copy?of?last?element

}

2. To use a class template, you pass the open types as template arguments. The class template is the instantiated(and compiled) for these types
3. For class templates, only those menber funcitons that are called are instantiated
This , of course, saves time and space. It has the additional benefit that you can instantiate a class even for those types that cannot perform all the operations of all the menber functions, as long as these member functions are not called.
Note that you have to put whitespace between the two closing? template brackets. If you don't do this, you are using operator>>,which results in a syntax error:
Stack<Stack<int>>?intStackStack;?//ERROR:>>is?not?allowed
4. You can specialize calss templates for certain types

template<>

class?Stack<std::string>?{

??private:

????std::deque<std::string>?elems;??//?elements

??public:

????void?push(std::string?const&);??//?push?element

????void?pop();?????????????????????//?pop?element

????std::string?top()?const;????????//?return?top?element

????bool?empty()?const?{????????????//?return?whether?the?stack?is?empty

????????return?elems.empty();

????}

};

void?Stack<std::string>::push?(std::string?const&?elem)

{

????elems.push_back(elem);????//?append?copy?of?passed?elem

}

void?Stack<std::string>::pop?()

{

????if?(elems.empty())?{

????????throw?std::out_of_range

????????????????("Stack<std::string>::pop():?empty?stack");

????}

????elems.pop_back();?????????//?remove?last?element

}

std::string?Stack<std::string>::top?()?const

{

????if?(elems.empty())?{

????????throw?std::out_of_range

????????????????("Stack<std::string>::top():?empty?stack");

????}

????return?elems.back();??????//?return?copy?of?last?element

}

ps：也就是所謂的特定版本，模板元編程中的關鍵。
5. You can partially specialize class templates for certain types
If more than one partial specilalization matches equally well, the declaration is ambiguous
6. You can define default values for class template parameters.These may refer to previous template parameters

posted on 2006-11-26 16:15 ningfangli 閱讀(164) 評論(0) 編輯收藏引用

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"C++Templates The Complete Guide"讀書筆記----Chapter 3

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