the denotational semantics approach uses least fixed points to obtain from a given program text a corresponding mathematical function, called its semantics. To this end, an artificial mathematical object, , is introduced, denoting the exceptional value "undefined".Given e.g. the program datatype int, its mathematical counterpart is defined as it is made a partially ordered set by defining for each and letting any two different members be uncomparable w.r.t. , see picture.

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