Struct SquareEdgeCoord

Represents a unique, canonical edge in a square grid, identified by the anchor cell coordinate and the edge direction (N or W).

Implements
Inherited Members
Namespace: Scylla.Core.Structures
Assembly: ScyllaCore.dll
Syntax
public readonly struct SquareEdgeCoord : IEquatable<SquareEdgeCoord>
Remarks

Each interior edge in a square grid is physically shared by two adjacent cells. To guarantee a single canonical address per edge the encoding stores only the N (top) and W (left) edges of each cell:

  • N edge of (c, r) - the horizontal edge at the top of cell (c, r), also the south edge of cell (c, r-1).
  • W edge of (c, r) - the vertical edge at the left of cell (c, r), also the east edge of cell (c-1, r).

To address the south edge of cell (c, r), use the N edge of (c, r+1). To address the east edge of cell (c, r), use the W edge of (c+1, r).

The static topology helpers (GetCellsNonAlloc(SquareEdgeCoord, Span<SquareCoord>), GetCornersNonAlloc(SquareEdgeCoord, Span<SquareCornerCoord>), GetEdgesOfCellNonAlloc(SquareCoord, Span<SquareEdgeCoord>)) all write into caller-supplied Span<T> buffers to remain allocation-free.

Constructors

SquareEdgeCoord(int, int, SquareEdgeDirection)

Creates a new square edge coordinate from an anchor cell and a direction.

Declaration
public SquareEdgeCoord(int col, int row, SquareEdgeDirection direction)
Parameters
Type Name Description
int col

The column of the anchor cell.
int row

The row of the anchor cell.
SquareEdgeDirection direction

The canonical edge direction: N for the top horizontal edge, or W for the left vertical edge.

Fields

Col

The column of the anchor cell that owns this edge.

Declaration
public readonly int Col
Field Value
Type Description
int

Direction

The direction of this edge relative to the anchor cell. N is the top horizontal edge; W is the left vertical edge.

Declaration
public readonly SquareEdgeDirection Direction
Field Value
Type Description
SquareEdgeDirection

Row

The row of the anchor cell that owns this edge.

Declaration
public readonly int Row
Field Value
Type Description
int

Methods

Equals(SquareEdgeCoord)

Determines whether this edge coordinate equals other.

Declaration
public bool Equals(SquareEdgeCoord other)
Parameters
Type Name Description
SquareEdgeCoord other

The edge coordinate to compare with.
Returns
Type Description
bool

true if Col, Row, and Direction are all equal; false otherwise.

Equals(object)

Determines whether this edge coordinate equals an arbitrary object.

Declaration
public override bool Equals(object obj)
Parameters
Type Name Description
object obj

The object to compare with. May be null.
Returns
Type Description
bool

true if obj is a SquareEdgeCoord with equal column, row, and direction values; false otherwise.
Overrides

GetCellsNonAlloc(SquareEdgeCoord, Span<SquareCoord>)

Writes the two cells that share edge into buffer.

Declaration
public static int GetCellsNonAlloc(SquareEdgeCoord edge, Span<SquareCoord> buffer)
Parameters
Type Name Description
SquareEdgeCoord edge

The edge whose sharing cells are requested.
Span<SquareCoord> buffer

A Span<T> of at least 2 elements to receive the two cell coordinates. If the span is smaller than 2, the method writes nothing and returns 0.
Returns
Type Description
int

The number of cell coordinates written into buffer: always 2 when the buffer is large enough, or 0 when the buffer has fewer than 2 elements.
Remarks

The two sharing cells are determined by the edge direction:

  • N edge of (c, r) - cells (c, r) and (c, r-1).
  • W edge of (c, r) - cells (c, r) and (c-1, r).

The returned coordinates are not bounds-checked against any particular grid; callers should validate them with IsInBounds(int, int) or IsInBounds(int, int) as needed.

GetCornersNonAlloc(SquareEdgeCoord, Span<SquareCornerCoord>)

Writes the two corner endpoints of edge into buffer.

Declaration
public static int GetCornersNonAlloc(SquareEdgeCoord edge, Span<SquareCornerCoord> buffer)
Parameters
Type Name Description
SquareEdgeCoord edge

The edge whose corner endpoints are requested.
Span<SquareCornerCoord> buffer

A Span<T> of at least 2 elements to receive the two corner coordinates. If the span is smaller than 2, the method writes nothing and returns 0.
Returns
Type Description
int

The number of corner coordinates written into buffer: always 2 when the buffer is large enough, or 0 when the buffer has fewer than 2 elements.
Remarks

The corner endpoints are determined by the edge direction:

  • N edge of (c, r) - corners (c, r) (northwest) and (c+1, r) (northeast).
  • W edge of (c, r) - corners (c, r) (northwest) and (c, r+1) (southwest).

Corner coordinates follow the convention described in SquareCornerCoord: corner (c, r) is the northwest vertex of cell (c, r).

GetEdgesOfCellNonAlloc(SquareCoord, Span<SquareEdgeCoord>)

Writes the four canonical edges that bound cell into buffer.

Declaration
public static int GetEdgesOfCellNonAlloc(SquareCoord cell, Span<SquareEdgeCoord> buffer)
Parameters
Type Name Description
SquareCoord cell

The cell whose four bounding edges are requested.
Span<SquareEdgeCoord> buffer

A Span<T> of at least 4 elements to receive the edge coordinates. If the span is smaller than 4, the method writes nothing and returns 0.
Returns
Type Description
int

The number of edge coordinates written into buffer: always 4 when the buffer is large enough, or 0 when the buffer has fewer than 4 elements.
Remarks

Every square cell is surrounded by four edges. Using the canonical N/W encoding, the four edges of cell (c, r) are:

  • North: (c, r, N)
  • West: (c, r, W)
  • East: (c+1, r, W)
  • South: (c, r+1, N)

The edges are written in the order North, West, East, South (indices 0-3).

GetHashCode()

Returns a hash code for this edge coordinate based on its column, row, and direction.

Declaration
public override int GetHashCode()
Returns
Type Description
int

A hash code suitable for use in hash-based collections such as Dictionary<TKey, TValue>.
Overrides

ToString()

Returns a human-readable string representation of this edge coordinate.

Declaration
public override string ToString()
Returns
Type Description
string

A string in the format (Col, Row, Direction), e.g. (2, 3, N).
Overrides

Operators

operator ==(SquareEdgeCoord, SquareEdgeCoord)

Returns true if left and right refer to the same canonical edge (equal column, row, and direction).

Declaration
public static bool operator ==(SquareEdgeCoord left, SquareEdgeCoord right)
Parameters
Type Name Description
SquareEdgeCoord left
SquareEdgeCoord right
Returns
Type Description
bool

operator !=(SquareEdgeCoord, SquareEdgeCoord)

Returns true if left and right refer to different edges.

Declaration
public static bool operator !=(SquareEdgeCoord left, SquareEdgeCoord right)
Parameters
Type Name Description
SquareEdgeCoord left
SquareEdgeCoord right
Returns
Type Description
bool

Implements

See Also