#include <iostream>
#include<cstring>
using namespace std;

char * strcat ( char * destination, const char * source, int );

int main() {

char str[20] = "hi";
char *pStr = str;
cout << pStr << endl;  // prints hi

char str2[20];
str2[0]='b';
str2[0]='b';
str2[1]='y';
str2[2]='e';
str2[3]='\0';

// what's wrong with:
//int len = str2.length(); //use strlen function!
//cout<<"length="<<len<<endl;

pStr=str2;
cout << str2 << endl;

if (pStr==str2) cout << "equal by addresses"<<endl;

char cpstr[10]="bye";
if(str2==cpstr) //compares addresses
    cout<<" also equal by addresses!"<<endl;

if(strcmp(str2, cpstr)==0) //compares contents
    cout<<" also equal by contents!"<<endl;

if(str2 > cpstr) //compares contents
    cout<<" first comes first"<<endl;


strcat(str, " ", 20);
strcat(str, str2, 20);
//this will fail since there is not enough space!
strcat(str, " computer class", 20);

cout<<str<<endl;

string cppstring;

cppstring="hello";  // assigning a c-string to a c++ string
cppstring=str2;     // same

// cannot assign to a c-string:    str2=cppstring;

// CAN compare a c-string and a c++ string
if(cppstring=="bye")
    cout<<"same!"<<endl;

// if either side of the operator is a c++ string then contents are compared
// cannot do this for 2 c-strings (use strcmp)
if (str2==cppstring)
    cout<<"same again!"<<endl;

//overloaded comparison operators
//alphabetic comparison
if(cppstring>"g")
    cout<<"bye is greater than g"<<endl;
if(cppstring<"g")
    cout<<"bye is less than g"<<endl;


return 0;
}


// we are writing our own strcat function to concatenate source to destination

char * strcat ( char * destination, const char * source, int destSize )
{

//find the last loc of destination
int i=0;
while (destination[i]!='\0')
   i++;

int sourceLen=0;
while (source[sourceLen]!='\0')
   sourceLen++;

//make sure destination has enough empty space to accommodate source!
if (sourceLen + i > destSize) //not enough space!
    return destination;


int j=0;
while (source[j]!='\0')
  {
   destination[i]=source[j];
   i++;
   j++;
  }

destination[i]='\0';

return destination;
}