export const enum DirectionArrowSymbol { NORTH = '^' , EAST = '>' , SOUTH = 'v' , WEST = '<' } export type HorizontalDirectionArrowSymbol = DirectionArrowSymbol . EAST | DirectionArrowSymbol . WEST ; export type VericalDirectionArrowSymbol = DirectionArrowSymbol . NORTH | DirectionArrowSymbol . NORTH ; export const isHorizontalDirectionArrowSymbol = ( symbol ) : symbol is HorizontalDirectionArrowSymbol => symbol === DirectionArrowSymbol . EAST || symbol === DirectionArrowSymbol . WEST ; export const isVericalDirectionArrowSymbol = ( symbol ) : symbol is VericalDirectionArrowSymbol => symbol === DirectionArrowSymbol . NORTH || symbol === DirectionArrowSymbol . SOUTH ; export const isDirectionArrowSymbol = ( symbol ) : symbol is DirectionArrowSymbol => isHorizontalDirectionArrowSymbol ( symbol ) || isVericalDirectionArrowSymbol ( symbol ) ;