web/lib/fmt.ts

/**
 * Format a fitness / score value. Returns "—" for null, undefined, NaN,
 * or +/-Infinity so the UI never throws on degenerate programs.
 */
export function fmtFit(x: number | null | undefined, digits = 2): string {
  if (typeof x === "number" && Number.isFinite(x)) return x.toFixed(digits);
  return "—";
}

/** Numeric value to use for sort / colour when the raw fitness isn't
 * finite. Pushes degenerate programs to the bottom of any ranking. */
export function fitnessForOrder(x: number | null | undefined): number {
  return typeof x === "number" && Number.isFinite(x) ? x : -Infinity;
}