A fair enumeration emits every required occurrence after finitely many computation steps. The inputs can be infinite; completeness does not mean waiting until they have all been exhausted. If two proper lazy lists alternate their next available entries, every occurrence reaches the output after finitely many swaps. In contrast, a nested list comprehension can remain forever in its first infinite inner list. Fairness concerns input occurrences, even when different occurrences happen to have equal values.
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