Binary Operator Overloading

Overloading == and !=

The member function eq() is defined as part of Object as:

int eq(Object o);

so that every class object has an eq().

If a struct has no eq() function declared for it, a bit compare of the contents of the two structs is done to determine equality or inequality.

Overloading <, <=, > and >=

The member function cmp() is defined as part of Object as:

int cmp(Object o);

so that every class object has a cmp().

If a struct has no cmp() function declared for it, attempting to compare two structs is an error.

Note: Comparing a reference to a class object against null should be done as:

if (a === null)

and not as:

if (a == null)

The latter is converted to:

if (a.cmp(null))

which will fail if cmp is a virtual function.

Rationale

• 
  Testing for equality can sometimes be a much more efficient operation than testing for less or greater than.
  
• 
  For some objects, testing for less or greater makes no sense. For these, override cmp() with:
  
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  class A
  
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  {
  
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  int cmp(Object o)
  
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  {
  
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  assert(0); // comparison makes no sense
  
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  return 0;
  
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  }
  
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  }