Add the Ackermann example

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (9233b27) 92.25% compared to head (eb1120a) 92.43%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1100 +/- ## ========================================== + Coverage 92.25% 92.43% +0.17% ========================================== Files 93 93 Lines 10640 10640 Branches 2479 2479 ========================================== + Hits 9816 9835 +19 + Misses 824 805 -19 ```

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