message: tweak Interval.size
diff: @@ -16,7 +16,7 @@ export const start = Tuple.fst;
  export const end = Tuple.snd;
  export const min = Tuple.fst;
  export function max(i: Tuple) { return Tuple.snd(i) - 1; }
  -export function size(i: Tuple) { return Tuple.snd(i) - Tuple.fst(i); }
  +export const size = Tuple.diff;
  export const hashCode = Tuple.hashCode;
  export const toString = Tuple.toString;
  