.TH G_EQUAL 2 "8 April 1991" "Demeter" "Demeter Software"
.SH NAME
g_equal \- send the generic equal message to an object.
.SH SYNOPSIS

virtual int Universal::
.I g_equal
( Universal* otherObject )

.SH DESCRIPTION

.I g_equal
performs a deep comparison for equality between the object to which
the message is sent and an argument object. This means that
.I g_equal
succeeds only if both objects are of the same type, they have the same
instantiated parts and each part succeeds when sent g_equal with the
corresponding part of the argument object. The receiving and the
argument objects must be a tree objects. That is, they cannot have any
cycles or shared subobjects.

.SH REDEFINITION
Since
.I g_equal
is a virtual function, it can be redefined at any user class. This
means that the user can modify the criterion by which any object of
some particular class is equal to any other object. As a technical
consideration, making g_equal 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 RETURN VALUES

.I g_equal
returns an integer 1 if it succeeds and an integer 0 otherwise. For
example:

Compound* iComp1 = new Compound();
.br
Compound* iComp2 = new Compound();
.br
Compound* iComp3;
.br
Compound* iComp4 = new Compound();

iComp1 = (Compound*)iComp1->g_parse("input1");
.br
iComp2 = (Compound*)iComp2->g_parse("input2");
.br
iComp3 = (Compound*)iComp1->g_copy();
.br
iComp4 = (Compound*)iComp2->g_parse("input2");

int a = iComp1->g_equal( iComp2 ); // returns 0, false
.br
int b = iComp1->g_equal( iComp3 ); // returns 1
.br
int c = iComp2->g_equal( iComp4 ); // returns 1
.br
int d = iComp3->g_equal( iComp4 ); // returns 0

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