definition
| - In every value space there is a notion of equality, for which the following rules hold:
- for any two instances (a, b) of values from the value space, either a is equal to b, denoted a = b , or a is not equal to b, denoted a ≠ b ;
- there is no pair of instances (a, b) of values from the value space such that both a = b and a ≠ b ;
- for every value a from the value space, a = a ;
- for any two instances (a, b) of values from the value space, a = b if and only if b = a ;
- for any three instances (a, b, c) of values from the value space, if a = b and b = c , then a = c .
On every datatype, the operation Equal is defined in terms of the equality property of the value space, by:
- for any values a, b drawn from the value space, Equal(a,b) is true if a = b , and false otherwise. [ISO11404]
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