NULL safe equality operator

[Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>]

Hi guys,

Does anyone know how I'd go about implementing the following MySQL 
operator in PostgreSQL?

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NULL-safe equal. This operator performs an equality comparison like the 
=  operator, but returns 1 rather than NULL if both operands are NULL, 
and 0 rather than NULL if one operand isNULL.

mysql> SELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL;
        -> 1, 1, 0
mysql> SELECT 1 = 1, NULL = NULL, 1 = NULL;
        -> 1, NULL, NULL

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Chris