In type theory and functional programming, a stream is a potentially infinite analog of a list, given by the coinductive definition:^[1][2]

data Stream α = Nil | Cons α (Stream α)

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Generating and computing with streams requires lazy evaluation, either implicitly in a lazily evaluated language or by creating and forcing thunks in an eager language. In total languages they must be defined as codata and can be iterated over using (guarded) corecursion.

• Coinduction