.TH G_CHECK 2 "2 October 1991" "Demeter" "Demeter Software"
.SH NAME
g_check \- send the generic check message to an object.
.SH SYNOPSIS

int Universal::
.I g_check
( char* objClassName )

.SH DESCRIPTION

.I g_check
checks whether the receiver is a legal object of class
.I objClassName.
If
.I objClassName
is not provided, the first class in the current class dictionary is
used. The receiving object must be a tree object. That is, it cannot
have any cycles or shared subobjects.
.I g_check
is a generic method implemented at class Universal and inherited by any
user class.

.SH ERROR MESSAGES

If the receiving object is a legal object of class
.I objClassName,
.I g_check
displays the message "GCHECK Success: this is a legal object of type
.I objClassName
". Otherwise, three error messages are displayed.

.TP 10
Diagnostic
An explanation of the error.
.TP
Production stack dump
A listing, in reverse order, of the productions in the grammar that
led to the point where the error occurred.
.TP
Error condition
The message "GCHECK Error: this is NOT a legal object of type
.I objClassName
" is displayed.
.LP

.SH EXAMPLE
Here is an example of how to use
.I g_check .

Compound* iCompound = new Compound();
.br
iCompound = someCompoundInstantiatingFunction();
.br

.br
if( iCompound->g_check() )
.br
   exit( -1 );
.br

Of course, in this example we could have used g_parse. But since a
successful send of g_parse always returns a legal object, sending
g_check becomes unnecessary. This example shows that
.I g_check
is most useful when instantiating objects with means other than g_parse.

.SH SEE ALSO
g_parse(2), g_equal(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