Programmer Defined [ ] operator.

Let's define a class for Strings.

stringx.h

#include "string.h";

const char EOS = '\0';

class String

{

public:

String();

String( const char cstr[] );

~String();

...

char operator[] ( int index ) const;

...

private:

char* string;

int size;

};

stringx.cpp

String::String()

{

string = new char[1];

string[0] = EOS;

size = 0;

}

String::String( const char cstr[] )

{

size = strlen( cstr );

string = new char[size+1];

strcpy( string, cstr );

}

String::~String()

{

delete string;

}

Let's define the [] operator for our String class.

char String::operator[] ( int index ) const

{

if ( index < 0 || index >= size )

throw out_of_range( "Index out of range" );

return string[index];

}

See exception handling (later...) for what throw does.

app.cpp

#include "stringx.h"

void main()

{

String str( "abcd" );

char ch = str[1];

}