ssrs gs1 128 ANAPPENDOPERATOR in Software

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The += operator is one of a series of arithmetic assignment operators that combine the arithmetic operators (+, -, *, etc.) with the assignment operator. Like most operators, the arithmetic assignment operators can be overloaded to perform whatever operations you want. However, it is unwise to define an overloaded operator to do anything that is not similar to the action of the original operator. The += operator is defined for integer types to be equivalent to the addition operator followed by the assignment operator. For example, the following two blocks have the same effect:

{ int n += m; } { int temp = m + n; int n = temp; }

The only difference is that the second block uses an extra int. In our String class, we overloaded the += operator to preserve this meaning, so that the following two blocks will have the same effect:

{ String s2 += sl; } ( String temp = sl + s2; int s2 = temp; }

Here is the overloaded += operator for our String class:

String& String::operator+=(const String& s) len += s.len; char* tempbuf = new char[len+l]; strcpy(tempbuf, buf); strcat(tempbuf, s.buf); delete [] buf; buf = tempbuf; return *this;

First it increments its len field by the length of the String object passed to it. Then it allocates the total number of bytes needed for the new string and holds this space in the temporary C-string tempbuf. Then, just as it does with the addition operator (page 280), it uses the strcpy ( > and strcat ( ) functions defined in the string. h header file to copy its buf to t empbuf and then append s . buf to it. Now it can release the memory allocated to its original buffer and then assign the t empbuf pointer to it.

This test driver invokes the + = operator to append the string I object name:

#include "String.h"

main0 { String name('Tharles Babbage"); tout << "name = [" << name c< "]\n"; name += " (1792-1871)"; tout << "name = [" << name << "]\n"; nasrre = [ChaxJes Babbage] name = [Charles Babbage (1792~187W

Note that the third constructor will be invoked to convert the C-string String object before it is passed to the += operator.

operator char*0 const;

is a conversion operator that converts a String object into a C-string. It has the reverse effect of the constructor

String (const char*);

CHAP. lo]

This conversion operator has a very simple implementation:

data member is the C-string that we want. -

Note that this conversion operator is an access function: it simply provides public access to the private data member buf. It is not really an inverse of the String (const char* ) constructor because it does not create a new C-string. As an access function, it merely provides public access to the buf C-string that already exists within the String object.

EXAMPLE 10.10 Testing the Conversion to C-String Operator #include '5tring.h"

main0 1 String name("John von Neumann"); tout << "name = ['I c< name << "]\n"; char* s = name; tout << "s = [ 'I << s -c-c 'I ] \n" ; nae = [John van Neumann] s = [John van Neumann]

Here is the overloaded subscript operator for our String class:

char& String: :operator[] (unsigned i) const buf[i];

EXAMPLE 10.11 Testing the Subscript Operator #include '5tring.h"

main0 { String name("Charles Babbage"); tout -x "name = ['I << name << II]\W; tout << "name[8] = ['I << name[8] << "]\n"; name[8] = 'Cl; tout << "name[8] = [I' << name[8] << "]\nI'; tout -x "name = ['I << name cc "]\n";