is mentioned by

Def leaf_value(t) == Case(t) Case tree_leaf(l) => l Default => True	[leaf_value]
Def is_leaf(t) == Case(t) Case tree_leaf(l) => true Default => false	[is_leaf]
Def t_iterate(l;n;t) Def == Case(t) Def == Case x;y => Def == Casen(t_iterate(l;n;x),t_iterate(l;n;y)) Def == Case tree_leaf(x) => Def == Casel(x) Def == Default => True Def (recursive)	[t_iterate]

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