Introduction to C++ Templates and Exceptions.ppt

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1、Introduction to C+ Templates and Exceptions,C+ Function Templates C+ Class Templates,C+ Function Templates,Approaches for functions that implement identical tasks for different data types Nave Approach Function Overloading Function Template Instantiating a Function Templates,Approach 1: Nave Approac

2、h,create unique functions with unique names for each combination of data types difficult to keeping track of multiple function names lead to programming errors,Example,void PrintInt( int n ) cout “*Debug“ endl;cout “Value is “ n endl; void PrintChar( char ch ) cout “*Debug“ endl;cout “Value is “ ch

3、endl; void PrintFloat( float x ) void PrintDouble( double d ) ,PrintInt(sum);PrintChar(initial);PrintFloat(angle);,To output the traced values, we insert:,Approach 2:Function Overloading (Review),The use of the same name for different C+ functions, distinguished from each other by their parameter li

4、sts,Eliminates need to come up with many different names for identical tasks.Reduces the chance of unexpected results caused by using the wrong function name.,Example of Function Overloading,void Print( int n ) cout “*Debug“ endl;cout “Value is “ n endl; void Print( char ch ) cout “*Debug“ endl;cout

5、 “Value is “ ch endl; void Print( float x ) ,Print(someInt); Print(someChar); Print(someFloat);,To output the traced values, we insert:,Approach 3: Function Template,A C+ language construct that allows the compiler to generate multiple versions of a function by allowing parameterized data types.,Tem

6、plate FunctionDefinition,FunctionTemplate,TemplateParamDeclaration: placeholder,class typeIdentifier typename variableIdentifier,Example of a Function Template,templatevoid Print( SomeType val ) cout “*Debug“ endl;cout “Value is “ val endl; ,Print(sum); Print(initial); Print(angle);,To output the tr

7、aced values, we insert:,Template parameter (class, user defined type, built-in types),Template argument,Instantiating a Function Template,When the compiler instantiates a template, it substitutes the template argument for the template parameter throughout the function template.,Function (FunctionArg

8、List),TemplateFunction Call,A more complex example,template void sort(vector ,Summary of Three Approaches,Nave Approach Different Function Definitions Different Function Names,Function Overloading Different Function Definitions Same Function Name,Template Functions One Function Definition (a functio

9、n template) Compiler Generates Individual Functions,Class Template,A C+ language construct that allows the compiler to generate multiple versions of a class by allowing parameterized data types.,Template ClassDefinition,Class Template,TemplateParamDeclaration: placeholder,class typeIdentifier typena

10、me variableIdentifier,Example of a Class Template,template class GList public:bool IsEmpty() const;bool IsFull() const;int Length() const;void Insert( /* in */ ItemType item );void Delete( /* in */ ItemType item );bool IsPresent( /* in */ ItemType item ) const;void SelSort();void Print() const;GList

11、(); / Constructorprivate:int length;ItemType dataMAX_LENGTH; ;,Template parameter,Instantiating a Class Template,Class template arguments must be explicit. The compiler generates distinct class types called template classes or generated classes. When instantiating a template, a compiler substitutes

12、the template argument for the template parameter throughout the class template.,Instantiating a Class Template,/ Client codeGList list1; GList list2; GList list3;list1.Insert(356); list2.Insert(84.375); list3.Insert(“Muffler bolt“);,To create lists of different data types,GList_int list1; GList_floa

13、t list2; GList_string list3;,template argument,Compiler generates 3 distinct class types,Substitution Example,class GList_int public:void Insert( /* in */ ItemType item );void Delete( /* in */ ItemType item );bool IsPresent( /* in */ ItemType item ) const;private:int length;ItemType dataMAX_LENGTH;

14、;,int,int,int,int,Function Definitions for Members of a Template Class,template void GList:Insert( /* in */ ItemType item ) datalength = item;length+; ,/after substitution of float void GList:Insert( /* in */ float item ) datalength = item;length+; ,Another Template Example: passing two parameters,t

15、emplate class Stack .T bufsize;Stack mystack;,non-type parameter,Standard Template Library,In the late 70s Alexander Stepanov first observed that some algorithms do not depend on some particular implementation of a data structure but only on a few fundamental semantic properties of the structure Dev

16、eloped by Stepanov and Lee at HP labs in 1992 Become part of the C+ Standard in 1994,Whats in STL?,Container classes: vector, list, deque, set, map, and etc A large collection of algorithms, such as reverse, swap, heap, and etc.,Vector,A sequence that supports random access to elements Elements can

17、be inserted and removed at the beginning, the end and the middle Constant time random access Commonly used operations begin(), end(), size(), , push_back(), pop_back(), insert(), empty(),Example of vectors,/ Instantiate a vector vector V;/ Insert elements V.push_back(2); / v0 = 2 V.insert(V.begin(),

18、 3); / V0 = 3, V1 = 2/ Random access V0 = 5; / V0 = 5/ Test the size int size = V.size(); / size = 2,Take Home Message,Templates are mechanisms for generating functions and classes on type parameters. We can design a single class or function that operates on data of many typesfunction templates class templates,