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ordered pair

A collection of two objects such that one can be distinguished as the first element and the other as the second element. An ordered pair with first element a and second element b is usually written as (a, b). Two such ordered pairs (a1, b1) and (a2, b2) are equal if and only if a1 = a2 and b1 = b2. Ordered triples and ordered n-tuples (ordered lists of n terms) are defined in the same way. An ordered triple (a, b, c) can be defined as (a , (b, c)), i.e. as two nested pairs.

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