.TH G_CODE 2 "3 May 1991" "Demeter" "Demeter Software"

.SH NAME
g_code \- generates C++ code that creates an identical copy of the object

.SH SYNOPSIS

      char* 
.I g_code
( char* );
.br
      char* 
.I g_code
( ofstream& );
.br
      virtual char*
.I g_code
( int&,ofstream& );

.SH DESCRIPTION

.I g_code
generates C++ code that makes, when executed, an instance of an object
which is an identical copy of the object to which the message was
sent.  The code generated can then be integrated into a C++ program.
The receiving object must be a tree object. That is, it cannot have
any cycles or shared subobjects.

.SH ARGUMENTS

.RS 5.0
char*
.I g_code
( char* )
.RS 6.0
The input argument is the name of the file you want to store
the generated C++ code.
.RE
.RE

.RS 5.0 
char*
.I g_code
( ofstream& )    

.RS 6.0 
The input argument is the 
.I ofstream
variable to which you want to write
the generated C++ code. 
.RE 
.RE

.RS 5.0  
virtual char* 
.I g_code
( int& idCnt,ofstream& )

.RS 6.0
.I g_code
generates a number of temporary variables. The names for each of these
variable start with "i" followed by the class name of an object and ends
with a number.
.I idCnt
refers to this number. Every time g_code generates a variable, it will
increment the value of this number.

If you use
.I char* g_code( ofstream& ),
the number starts from 1.

The second argument is the 
.I ofstream
variable to which you want to write
the generated C++ code.  
.RE  
.RE

.SH RETURN VALUES

.I g_code
returns a character pointer that points to a string that contains the
name of the variable where the copy of the object is stored. For
example:

Compound* iCompound = new Compound();
.br
iCompound = (Compound*)iCompound->g_parse("demeter-input");
.br
char* variableName = iCompound->g_code("code.c");

In file
.I code.c,
there is some C++ code to create an identical copy of
Compound-object, iCompound.
The address of the resulting object is assigned to the variable
whose name is stored in 
.I variableName.

Notice that as a side effect
.I g_code
will print the code to the stream or file with filename given. As
a consequence, if you plan to use the returned value of
.I g_code,
namely
.I variableName
to print it to the same stream or file, you should be careful to first
store the name in a variable and then print it, to give
.I g_code
time to do its printing and then return its value. The following example
shows how NOT to use the value returned by
.I g_code.
Suppose the variable
.I codeStream
of type ostream is used to hold the stream of file
.I code.c.

Compound* iCompound = new Compound();
.br
iCompound = (Compound*)iCompound->g_parse("demeter-input");
.br
codeStream << "iCompound->g_equal("
.br
           << iCompound->g_code("code.c")       // WRONG !!!
.br
           << ");\en\&";

Here, the string "iCompund->g_equal" is printed first to the stream,
then the side effect of
.I g_code,
and then the value of
.I g_code,
which is not what is intended. The correct way of doing it would be as
follows.

Compound* iCompound = new Compound();
.br
iCompound = (Compound*)iCompound->g_parse("demeter-input");
.br
char* variableName = iCompound->g_code("code.c");
.br
codeStream << "iCompound->g_equal("
.br
           << variableName
.br
           << ");\en\&";  // OK


.SH REDEFINITION
Since
.I g_code
with the interface
.I char* g_code( int&,ofstream& ),
is a virtual function, it can be redefined at any user class. This
means that the user can change the code
.I g_code
generates for any particular object. As a technical consideration,
making
.I g_code
virtual allows to define it recursively and to give the termination
condition as a redefinition at the terminal classes DemIdent, DemNumber,
DemReal, DemString, and DemText.


.SH SEE ALSO
g_parse(2), g_equal(2), terminal(2), g_copy(2)

.SH REFERENCES 

.I User Manual for The C++ Demeter System
.br
Walter L. Hursch
.br
Northeastern University, 1993

.I The Annotated C++ Reference Manual
.br
Margaret A. Ellis and Bjarne Stroustrup
.br
Addison-Wesley, 1990

.I C++ Primer
.br
Stanley B. Lippman
.br
Addison-Wesley, 1989