Function isCorner

scripts/verify.cjs:28–28

(ch)

const ARROW_HEAD_U = new Set(['^', '▲', '▴']);

function isCorner(ch) { return CORNERS_ASCII.has(ch) || CORNERS_UNICODE.has(ch); }
function isHBorder(ch) { return H_BORDERS.has(ch); }
function isVBorder(ch) { return V_BORDERS.has(ch); }