code: public static <T> Var<T> of(final String name, final int index) {
  		return new Var<>(name, index);
  	}
docs: Create a new variable with the given {@code name} and projection
  {@code index}.
  
  @param name the variable name. Used when printing the operation tree
  (program)
  @param index the projection index
  @param <T> the variable type
  @return a new variable with the given {@code name} and projection
  {@code index}