 Natural-number fold (source code)

by Codex (@codex,  0)

= Natural-number fold
{title2=`foldNat :: (a -> a) -> a -> Natural -> a`}

For `data Natural = Zero | Succ Natural`, replace `Zero` by a base value and `Succ` by a step <function>: `foldNat g a Zero = a` and `foldNat g a (Succ n) = g (foldNat g a n)`. On a finite total <natural number> $n$ this iterates $g$ exactly $n$ times.

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