convert between ordinary strings and class String
#include <iostream>
using namespace std;
#include <string.h>
class String
{
private:
enum { SZ = 80 };
char str[SZ];
public:
String() { str[0] = "\0"; }
String( char s[] ) { strcpy(str, s); }
void display() const { cout << str; }
operator char*() { return str; }
};
int main()
{
String s1;
char xstr[] = "this is a test";
s1 = xstr;
s1.display();
String s2 = "this is another test";
cout << static_cast<char*>(s2);
cout << endl;
return 0;
}Define and use a string class
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <string>
#include <iostream>
#include <cctype>
/* replace functions of the standard char_traits<char>
* so that strings behave in a case-insensitive way
*/
struct ignorecase_traits : public std::char_traits<char> {
// return whether c1 and c2 are equal
static bool eq(const char& c1, const char& c2) {
return std::toupper(c1)==std::toupper(c2);
}
// return whether c1 is less than c2
static bool lt(const char& c1, const char& c2) {
return std::toupper(c1)<std::toupper(c2);
}
// compare up to n characters of s1 and s2
static int compare(const char* s1, const char* s2,
std::size_t n) {
for (std::size_t i=0; i<n; ++i) {
if (!eq(s1[i],s2[i])) {
return lt(s1[i],s2[i])?-1:1;
}
}
return 0;
}
// search c in s
static const char* find(const char* s, std::size_t n,
const char& c) {
for (std::size_t i=0; i<n; ++i) {
if (eq(s[i],c)) {
return &(s[i]);
}
}
return 0;
}
};
// define a special type for such strings
typedef std::basic_string<char,ignorecase_traits> icstring;
/* define an output operator
* because the traits type is different than that for std::ostream
*/
inline
std::ostream& operator << (std::ostream& strm, const icstring& s)
{
// simply convert the icstring into a normal string
return strm << std::string(s.data(),s.length());
}
int main()
{
using std::cout;
using std::endl;
icstring s1("hallo");
icstring s2("otto");
icstring s3("hALLo");
cout << std::boolalpha;
cout << s1 << " == " << s2 << " : " << (s1==s2) << endl;
cout << s1 << " == " << s3 << " : " << (s1==s3) << endl;
icstring::size_type idx = s1.find("All");
if (idx != icstring::npos) {
cout << "index of \"All\" in \"" << s1 << "\": "
<< idx << endl;
}
else {
cout << "\"All\" not found in \"" << s1 << endl;
}
}hallo == otto : false
hallo == hALLo : true
index of "All" in "hallo": 1
strings defined using array and pointer notation
#include <iostream>
using namespace std;
int main(){
char str1[] = "Defined as an array";
char* str2 = "Defined as a pointer";
cout << str1 << endl;
cout << str2 << endl;
str2++;
cout << str2 << endl;
return 0;
}Your own string class
#include<iostream.h>
#include<string.h>
#include<stdlib.h>
class String
{
char *p;
int length;
public:
String();
String(char *str,int len);
char *getstring(){return p;}
int getlength(){return length;}
};
String::String()
{
p=new char[255];
if(!p)
{
cout<<"Allocation erroe\n";
exit(1);
}
*p="\0";
length=255;
}
String::String(char * str,int len)
{
if(strlen(str)>=len)
{
cout<<"Allcation too little memory! \n";
exit(1);
}
p=new char[len];
if(!p)
{
cout<<"Allocation error\n";
exit(1);
}
strcpy(p,str);
length=len;
}
main()
{
String ob1;
String ob2("This is a string.",100);
cout<<"ob1:"<<ob1.getstring()<<"-Allocation length:";
cout<<ob1.getlength()<<"\n";
cout<<"ob2:"<<ob2.getstring()<<"-Allocation length:";
cout<<ob2.getlength()<<"\n";
return 0;
}ob1:-Allocation length:255
ob2:This is a string.-Allocation length:100
