not functional (as defined in ) and thus not well defined as a function. Colloquially, the "function" is also called ambiguous at point (although there is per definitionem never an "ambiguous function"), and the original "definition" is pointless.

Despite these subtle logical problems, it is quite common to use the term definition (without apostrophes) for "definitions" of this kind, for three reasons:

# It provides a handy shorthand of the two-step approach.
# The relevant mathematical reasoning (i.e., step 2) is the

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