The name undefined is a reserved word in Maple that can be produced and propagated in various ways, usually as the result of attempting to carry out an operation which cannot result in a number for the given operands.
undefined's typically result from operations in which one or more operands are undefined, or, in the absence of a trap (see events), from invalid operations or mathematical operations for which no single numeric value can represent the result.
In floating-point computations, the value Float(undefined) corresponds to the IEEE arithmetic representation for Not-a-Number (NaN).
undefined's from different computation environments (exact, software floats, etc.) are converted to the relevant computation environment when they occur in a mixed computation.
The Boolean evaluation of evalb(undefined <> undefined) always returns false.
To test for exactly the value undefined, as opposed to any of its variants, such as Float(undefined) or undefined+I*undefined, use the test type(expr, NumericClass(undefined)).
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