Variable getColConst

This is a more efficient version of getPosition.map(t => t[1]). This can be useful in combination with withIndent and getIndent, like this:

const checkIndent: P.Parser<P.Unit> = P.succeed(
  (indent: number) => (column: number) => indent <= column
 )
  .apply(P.getIndent)
  .apply(P.getCol)
  .andThen((isIdented) => {
    if (isIdented) {
      return P.succeed(P.Unit);
    } else {
      return P.problem("expecting more spaces");
    }
  });

So the checkIndent parser only succeeds when you are "deeper" than the current indent level.