C++ manipulation string using operators- programmingknow

C++ Manipulation of string using operators

ANSI C implements string character arrays, pointers and string functions. There are no operators for manipulation the strings. once of the main drawbacks of string manipulations in C is that whenever a string is to be copied, The programmer must fist determine its length and allocate the required amount of memory

Although these limitations exist in C++ as well, its permits us to create own definitions of operators that can be used to manipulation the any string very much similar to the decimal number(Recently ANSI C++ committee has added a new class called string to the C++) class library that supports all types of string manipulations. String manipulations using the string class are discuss in the next pages

For example, we shall be able to use statements like

string3=string1+string2;
if(string1>=string2) string =string1;

string can be defined as class objects which can be then manipulated like the built in types. since the strings vary greatly in size, we use new operator to allocate memory for each string and a pointer variable to point to the string array. Thus we must create string objects that can hold these two pieces of information, namely,locations and length which are necessary for strinf manipulations. A typical string class will look as follows

class string
{
char *p; // pointer to string
int len; // length of string
public:
……. // member functions
…… // to initialize and
……. // manipulate strings
};

we shall consider an example to illustrate the application of overloaded operators to strings The example shown in program below overloads two operators, + and <= just to show how they are implemented. This can be extended to cover other operators as well

MATHMATICAL OPERATIONS ON STRINGS
#include <string.h> #include <iostream> class String { char *p; int len; public : String() // create null string { len=0; p=0; }; String(const char *s); // create string from arrays String(const String & s); // copy constructor ~String() // destructor { delete p; } //+ operator friend String operator+(const String &s,const String &t); // <= operator friend int operator<=(const String &s, const String &t); friend void show(const String s); }; String :: String(const char *s) { p=new char[len+1]; strcpy(p,s); } String:: String(const String &s) { len=s.len; p=new char[len+1]; strcpy(p,s.p); } // overloading + operator String operator +(const String &s, const String &t) { String temp; temp.len=s.len+t.len; temp.p=new char[temp.len+1]; strcpy(temp.p,s.p); strcat(temp.p,t.p); return(temp); } // overloading <= operator int operator<=(const String &s, const String &t) { int m=strlen(s.p); int n=strlen(t.p); if (m<=n) return (1); else return (0); } void show(const String s) { std::cout<<s.p; } int main() { String s1="new"; String s2="york"; String s3="delhi"; String t1,t2,t3; t1=s1; t2=s2; t3=s1+s3; std::cout << "\n t1="; show(t1); std::cout << "\n t2="; show(t2); std::cout << "\n"; std::cout << "\nt3="; show(t3); std::cout << "\n\n"; if (t1<=t3) { show(t1); std::cout << "Smaller than"; show(t2); std::cout << "\n"; } else { show(t3); std::cout << "smaller than "; show(t1); std::cout << "\n"; } return 0; } ;