Trait sudoku_variants::constraint::RelativeCellConstraint[−][src]

pub trait RelativeCellConstraint {
    const RELATIVE_COORDINATES: &'static [(isize, isize)];
    fn is_forbidden(&self, reference_cell: usize, other_cell: usize) -> bool { ... }
}

A trait for Constraints that are defined by having no forbidden numbers in some relative configuration to the reference cell. Whether a number is forbidden is defined by RelativeCellConstraint::is_forbidden, which is a boolean relation between the reference cell and the other cell. By default, this checks for equality.

As an example, the constraint that no diagonally adjacent cells have the same number may be formulated as a RelativeCellConstraint with the relative coordinates [(-1, -1), (-1, +1), (+1, -1), (+1, +1)], with the default equality being used for is_forbidden.

Associated Constants

const RELATIVE_COORDINATES: &'static [(isize, isize)][src]

A slice of coordinates relative to the cell in question that must not contain the same number.

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Provided methods

fn is_forbidden(&self, reference_cell: usize, other_cell: usize) -> bool[src]

Given the contents of the reference cell and one other cell that is removed by one set of coordinates specified in RelativeCellConstraint::RELATIVE_COORDINATES, this method determines whether the reference cell violates the constraint. Since it is assumed that an empty cell cannot violate the constraint, this method is only called if both cells contain a number.

As an example, for ordinary constraints such as the no-knight’s-move- constraint, this is usually an equality check. A cell removed by a knight’s move may not be equal to the reference cell. This is actually the default behavior for this method.

However, in some situations this may be different. As an example, for the no-adjacent-consecutive-constraint, this is a predicate that determines whether the two numbers are consecutive.

Arguments

  • reference_cell: The cell which is currently tested, i.e. relative to which the coordinates are defined.
  • other_cell: A cell removed from the reference_cell by a set of coordinates from RelativeCellConstraint::RELATIVE_COORDINATES.
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Implementors

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