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|context> => |context: factorial>

supported-ops |0> => |op: fact>
fact |0> => |1>

supported-ops |*> => |op: n-1> + |op: fact>
n-1 |*> #=> arithmetic(|_self>,|->,|1>)
fact |*> #=> arithmetic( |_self>, |*>, fact n-1 |_self>)
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