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Showing posts from 2009

MBCS/Unicode enabled C++ string class.

TCHAR, the generic text mapping data type. This is Microsoft specific extension and is not ANSI-compatible. I have used this extension to create my small prototype MBCS/Unicode compatible class. This class consists of all the basic functionality required to represent a minimal string class. I have given the name for this class as "CStringUNI". // Header File #pragma once const int INIT_ALLOC_SIZE = 10; class CStringUNI { private: TCHAR *m_szBuffer; TCHAR *AllocateMemory(size_t size); public: CStringUNI(); CStringUNI(const CStringUNI&); CStringUNI(const TCHAR*); CStringUNI& operator=(const TCHAR*); CStringUNI& operator=(const CStringUNI&); CStringUNI& operator+=(const CStringUNI&); // Access Operator TCHAR operator[](const size_t n)const; TCHAR *GetBuffer() const; bool operator==(const TCHAR*) const; bool operator==(const CStringUNI&) const; virtual ~CStringUNI(); friend CStringUNI operator+(const CStringUNI& lhs, const

Importance of 'const' in C++

Lets declare a class 'Demo' class Demo { private: char a; void TestConst(char* const pData) const { // pData = "test"; // char* const protects // pData++; // pointer! // a = 'a'; // const for function // protects data member. } }; So, when we are working with C++, all data members irrespective of access specification, can be protected with 'const', appended to the declaration/definition.

Use of Memoization in Recursion

Memoization can be used to reduce function calls or computations. In the following example of Fibonacci series generation through C++, I will use normal recursion and then will change the same for memoization( ) to show the reduction of the function call. This is a simple demo implementation. static int counter = 0; int normalfibrecursion(int n) { if( n < 1) { return 0; } if(n == 1) { return 1; } if(n < 3) { return 1; } else { cout << "Call normalfibrecursion(" << n-2 << ") and normalfibrecursion(" << n-1 << ")\n"; counter++; return normalfibrecursion(n-2) + normalfibrecursion(n-1); } } In the above-mentioned simple prototype implementation for the Fibonacci series of n=10, the total function call comes to (54*2) times. This is usually very high and it will grow exponentially as n increases. Below mentioned picture demonstrates the fact: USE OF MEM

Generic Swap without using template

The idea behind this was, I wanted to write a function that will take two parameters of the same type as a parameter and then it will swap them. It is a kind of generic swap but without the use of a C++ template. So the best way of doing it using "void *" as a parameter. As we know "void *" represents any arbitrary type that actually eases my job of writing a generic swap function. So, the function signature can be like below: void swap(void *arg1, void *arg2); "void *" points to the starting address of the arbitrary location in the memory, irrespective of the bit pattern. Try to write the function like the below: void swap(void *arg1, void *arg2) { void temp = *arg1; arg1 = *arg2; *arg = temp; } Oops, this is full of errors. 1. We can't declare a variable of type "void". 2. "void *" can't be dereferenced. 3. We also interested in swapping values. So, number of bytes making up the values to be pass