fcefa40b6c
This is a very simple all different constraint, e.g. - It does not know that if there are more variables than candidates, it has reached a contradiction. - It does not know that, if there are as many variables as candidates, if only one variable can take on a candidate value, then all other candidates for that variable can be eliminated.
33 lines
1.0 KiB
Rust
33 lines
1.0 KiB
Rust
//! Constraint trait, and some common constraints.
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//!
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//! Note that all puzzle states visited during the solution search
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//! share the same set of constraints. This means that you cannot
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//! store additional information about the state (e.g. caches) in the
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//! constraint to reuse later.
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use ::{PuzzleSearch,Val,VarToken};
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/// Constraint trait.
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pub trait Constraint {
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/// Applied after a variable has been assigned.
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///
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/// Returns true if the search should continue with these variable
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/// assignments, or false if the constraint found a contradiction.
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fn on_assigned(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val)
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-> bool {
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true
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}
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/// Applied after a variable's candidates has been modified.
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///
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/// Returns true if the search should continue with these variable
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/// assignments, or false if the constraint found a contradiction.
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fn on_updated(&self, _search: &mut PuzzleSearch) -> bool {
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true
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}
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}
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pub use self::alldifferent::AllDifferent;
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mod alldifferent;
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