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Formats Example… A valuable routine to have is void Swap( int& an, int &b ) { int tmp = a; a = b; b = tmp; } Example… What happens in the event that we need to swap a twofold ? on the other hand a string ? For every one, we require distinctive capacity: void Swap( double& a, twofold &b ) {
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Formats .

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Example… A valuable routine to have is void Swap( int& an, int &b ) { int tmp = a; a = b; b = tmp; }

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Example… What happens in the event that we need to swap a twofold ? on the other hand a string ? For every one, we require diverse capacity: void Swap( double& a, twofold &b ) { double tmp = an; a = b; b = tmp; } void Swap( string& a, string &b ) { string tmp = an; a = b; b = tmp; }

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Generic Programming All these renditions of Swap are "isomorphic"/layout code for Swap for subjective sort T void Swap( T& a, T &b ) { T tmp = a; a = b; b = tmp; } Can we some way or another advise the compiler to utilize Swap with any sort T ?

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Templates The format watchword characterizes "layouts" Piece of code that will be recovered with various contentions every time template<class T>/T is a "sort contention" void Swap( T& a, T &b ) { T tmp = a; a = b; b = tmp; }

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Template Instantiation int fundamental() { int a = 2; int b = 3; Swap( a, b );/requires Swap( int&, int& ) } The compiler experiences Swap( int&, int& ) It instantiates the layout Swap with T = int and accumulates the code characterized by it

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Template Instantiation Different instantiations of a format can be created by the same system See Swap.cpp

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Templates & Compilation A format is an assertion The compiler performs punctuation checks just When a format is instantiated with particular contentions, then the produced code is assembled Implications : Template code must be unmistakable by the code that utilizations it (i.e., show up in .h document) Compilation blunders can happen just in a particular case (see Swap.cpp)

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Another Example…/Inefficient bland sort… template< class T > void Sort( T* start, T* end ) { for( ; start != end; begin++ ) for( T* q = begin+1; q != end; q++ ) if( *q < *begin ) Swap( *q, *begin ); } See [Sort.h, TestSort.cpp]

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More Complex Case… Suppose we need to abstain from composing administrator != for new classes layout <class T> bool operator!= (T const& lhs, T const& rhs) { return !(lhs == rhs); } When is this format utilized?

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More Complex Case… class MyClass { open: … bool operator==(MyClass const & rhs) const; … }; … int a, b; … if( a != b )/utilizes worked as a part of operator!=(int,int) … MyClass x,y; if( x != y )/utilizes layout with T = MyClass …

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When Templates are Used? At the point when the compiler experiences … f( a, b ) … Search for a capacity f() with coordinating sort signature If not discovered, look for a layout capacity that can be instantiated with coordinating sorts

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Generic Classes? Assume we execute a class StrList that keeps up a rundown of strings See StrList.h and StrList.cpp The real code for keeping up the rundown has nothing to do with the particulars of the string sort Can we have a non specific usage of records?

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Class Templates template<class T> class MyList { … }; … MyList<int> intList;/T = int MyList<string> stringList;/T = string

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Class Templates Code like normal code: Add template<… > explanation before every top-level build Use format contention as sort in class definition Implementation of techniques, to some degree more perplexing grammar See MyList.h TestMyList.h

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Constructing a List We need to instate a rundown from an exhibit We can compose a strategy that gets a pointer to the cluster, and a size contention int array[] = { 1, 2, 3, 4, 5, 6 }; MyList<int> list; list.copy( exhibit, 6 ); Alternative: utilize a pointer to starting position and one to the position after the last list.copy( cluster, array+6 ); This structure is more adaptable (as we should see)

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Constructing a List/Fancy duplicate from exhibit template< class T > MyList<T>::copy( T const* start, T const* end ) { T const* p; for( p = start; p != end; p++ ) pushBack(*p); }

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Pointer Paradigm Code like: T * p; for( p = start; p != end; p++ ) { //Do something with *p … } Applies to all components in [begin,end-1] Common in C/C++ projects Can we stretch out it to different holders?

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Iterator Object that carries on simply like a pointer Allows to repeat over components of a holder Example: MyList<int> L; … MyList<int>::iterator i; for( i = L.begin(); i != L.end(); i++ ) cout << " " << *i << "\n";

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Iterators To imitate pointers, we require: duplicate constructor administrator = (duplicate) administrator == (look at) administrator * (access esteem) operator++ (increase)

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MyList<T> iterator Keep a pointer to a hub class iterator { … private: Node m_pointer; }; Provide exemplification, since through such an iterator we can\'t change the structure of the rundown See MyListWithIterators.h

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Side Note operator++ In C we can utilize ++ in two structures: prefix documentation ++x increase x bring x \'s esteem postfix documentation x++ get x \'s esteem increase x How would we be able to actualize both variations?

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Operator++ Prefix structure: T& T::operator++(); Postfix structure T T::operator++(int);/sham contention! Note diverse return sorts See MyListWithIterators.h

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Initializing a List We now need to instate a rundown from utilizing parts of another rundown Something like template< class T > MyList<T>::copy( iterator start, iterator end ) { iterator p; for( p = start; p != end; p++ ) pushBack(*p); }

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Generic Constructor The code for replicating utilizing T* MyList<T>::iterator are basically indistinguishable deliberately - iterators mirror pointers Can we compose the code once?

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Template inside a format layout < class T > class MyList { … template< class Iterator > copy( Iterator start, Iterator end ) { for( Iterator p = start; p != end; p++ ) pushBack(*p); } … };

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Copy Method MyList<T>::copy() can be instantiated with various sorts pointer to T MyList<T>::iterator Iterators of other information structures that contain objects of sort T

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Template Variations Can get steady contentions template< class T, int Size = 1024> class Buffer { … private: T m_values[Size]; }; … Buffer<char> Buff1; Buffer<char,1024> Buff2;/same as Buff1 Buffer<int, 256> Buff3;

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Template and Types Buffer is not a sort Buffer<char,1024> is a sort Buffer<char>, buffer<char,1024> are two names for the same sort Buffer<char,256> is an alternate sort

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Class Templates - Recap Provides support for bland programming Parameters are either sorts or constants. Default qualities can be indicated Depends just on the properties it utilizes from its parameter sorts Resulting classes might be exceptionally proficient, however code size might be bigger Difficult to compose, keep up and investigate Class layout over-burdening is inconceivable

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Summary Alternative component to polymorphism Write & Debug solid illustration (e.g., StringList) before summing up to a format Understand iterators and other "assistant" classes Foundation for C++ standard library (STL)

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Things to peruse about Standard Library <string> – execution of string <algorithm> - calculations (sort, swap, and so forth.) <utility> - social administrators

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