pub type Computation = fn(&[Option<i128>]) -> Option<i128>;Expand description
A number worked out from the constants a pattern matched.
Handed one entry per binding, the same as a Guard is, and for the same reason: the
computation is written in the names the pattern bound and those are positions by the time it
runs. It gives nothing back when a binding it reads is not a constant, which is the answer a
guard gives as false, and the rule does not fire.