code: public NumberExpression<T> floor() {
          if (floor == null) {
              floor = Expressions.numberOperation(getType(), MathOps.FLOOR, mixin);
          }
          return floor;
      }
docs: Create a {@code floor(this)} expression
  
  <p>Returns the largest (closest to positive infinity)
  {@code double} value that is less than or equal to the
  argument and is equal to a mathematical integer.</p>
  
  @return floor(this)
  @see java.lang.Math#floor(double)