export const enum DirectionCardinalLiteralLetter { NORTH = 'U' , EAST = 'R' , SOUTH = 'D' , WEST = 'L' } export type HorizontalDirectionCardinalLiteralLetter = DirectionCardinalLiteralLetter . EAST | DirectionCardinalLiteralLetter . WEST ; export type VericalDirectionCardinalLiteralLetter = DirectionCardinalLiteralLetter . NORTH | DirectionCardinalLiteralLetter . NORTH ; export const isHorizontalDirectionCardinalLiteralLetter = ( symbol ) : symbol is HorizontalDirectionCardinalLiteralLetter => symbol === DirectionCardinalLiteralLetter . EAST || symbol === DirectionCardinalLiteralLetter . WEST ; export const isVericalDirectionCardinalLiteralLetter = ( symbol ) : symbol is VericalDirectionCardinalLiteralLetter => symbol === DirectionCardinalLiteralLetter . NORTH || symbol === DirectionCardinalLiteralLetter . SOUTH ; export const isDirectionCardinalLiteralLetter = ( marker ) : marker is DirectionCardinalLiteralLetter => isHorizontalDirectionCardinalLiteralLetter ( marker ) || isVericalDirectionCardinalLiteralLetter ( marker ) ;